The Knowledge, London’s Legendary Taxi-Driver Test, Puts Up a Fight in the Age of GPS



November 10, 2014 9:00 am


The examination to become a London cabby is possibly the most difficult test in the world — demanding years of study to memorize the labyrinthine city’s 25,000 streets and any business or landmark on them. As GPS and Uber imperil this tradition, is there an argument for learning as an end in itself?


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The posterior hippocampus, the area of the brain known to be important for memory, is bigger in London taxi drivers than in most people.

The posterior hippocampus, the area of the brain known to be important for memory, is bigger in London taxi drivers than in most people.Credit Photograph by Anthony Cotsifas. Prop stylist: Victoria Petro Conroy


At 10 past 6 on a January morning a couple of winters ago, a 35-year-old man named Matt McCabe stepped out of his house in the town of Kenley, England, got on his Piaggio X8 motor scooter, and started driving north. McCabe’s destination was Stour Road, a small street in a desolate patch of East London, 20 miles from his suburban home. He began his journey by following the A23, a major thruway connecting London with its southern outskirts, whose origins are thought to be ancient: For several miles the road follows the straight line of the Roman causeway that stretched from London to Brighton. McCabe exited the A23 in the South London neighborhood of Streatham and made his way through the streets, arriving, about 20 minutes after he set out, at an intersection officially called Windrush Square but still referred to by locals, and on most maps, as Brixton Oval. There, McCabe faced a decision: how to plot his route across the River Thames. Should he proceed more or less straight north and take London Bridge, or bear right into Coldharbour Lane and head for “the pipe,” the Rotherhithe Tunnel, which snakes under the Thames two miles downriver?

“At first I thought I’d go for London Bridge,” McCabe said later. “Go straight up Brixton Road to Kennington Park Road and then work my line over. I knew that I could make my life a lot easier, to not have to waste brainpower thinking about little roads — doing left-rights, left-rights. And then once I’d get over London Bridge, it’d be a quick trip: I’d work it up to Bethnal Green Road, Old Ford Road, and boom-boom-boom, I’m there. It’s a no-brainer. But no. I was thinking about the traffic, about everyone going to the City at that hour of the morning. I thought, ‘What can I do to skirt central London?’ That was my key decision point. I didn’t want to sit in the traffic lights. So I decided to take Coldharbour Lane and head for the pipe.”

McCabe turned east on Coldharbour Lane, wending through the neighborhoods of Peckham and Bermondsey before reaching the tunnel. He emerged on the far side of the Thames in Limehouse, and from there his three-mile-long trip followed a zigzagging path northeast. “I came out of the tunnel and went forward into Yorkshire Road,” he told me. “I went right into Salmon Lane. Left into Rhodeswell Road, right into Turners Road. I went right into St. Paul’s Way, left into Burdett Road, right into Mile End Road. Left Tredegar Square. I went right Morgan Street, left Coborn Road, right into Tredegar Road. That gave me a forward into Wick Lane, a right into Monier Road, right into Smeed Road — and we’re there. Left into Stour Road.”


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Over three years, Matt McCabe logged more than 50,000 miles on motorbike and foot within the city, the equivalent of two circumnavigations of the Earth, while studying to become a London taxi driver.

Over three years, Matt McCabe logged more than 50,000 miles on motorbike and foot within the city, the equivalent of two circumnavigations of the Earth, while studying to become a London taxi driver.Credit Rory Van Millingen


We were there, on Stour Road. It was a cold day, with temperatures hovering just above freezing, and snow in the forecast. For McCabe, on his bike, the wind chill made it feel considerably colder. He was dressed for the weather: a thermal shirt, a sweater, an insulated raincoat, Gore-Tex pants pulled over his jeans, gloves, work boots, a knit cap under his motorcycle helmet. McCabe is a tall man, about 6-foot-2, and he is solidly built, like a central defender on a soccer team. He’s handsome, with a wide smile and blond hair. He speaks in short sentences, snappy and definitive, especially when talking about London. We were in Hackney Wick, an industrial area adjacent to Queen Elizabeth Olympic Park, where the 2012 Olympic Games were held. Stour Road sits in a particularly remote corner of the neighborhood — a few wind-lashed streets, lined with warehouses, hemmed in by canals and a highway flyover.

“They call this area Fish Island,” McCabe said. “I’m not much of a fisherman, but many of the roads here are named for fishes — freshwater fishes, I believe. So just here you’ve got Bream Street.” He gestured down a road where a lumberyard was set back behind a corrugated metal fence. “Follow that to the end, you’ll come to Dace Road. You’ve got Roach Road. All names of fishes.”

McCabe had spent the last three years of his life thinking about London’s roads and landmarks, and how to navigate between them. In the process, he had logged more than 50,000 miles on motorbike and on foot, the equivalent of two circumnavigations of the Earth, nearly all within inner London’s dozen boroughs and the City of London financial district. He was studying to be a London taxi driver, devoting himself full-time to the challenge that would earn him a cabby’s “green badge” and put him behind the wheel of one of the city’s famous boxy black taxis.

Actually, “challenge” isn’t quite the word for the trial a London cabby endures to gain his qualification. It has been called the hardest test, of any kind, in the world. Its rigors have been likened to those required to earn a degree in law or medicine. It is without question a unique intellectual, psychological and physical ordeal, demanding unnumbered thousands of hours of immersive study, as would-be cabbies undertake the task of committing to memory the entirety of London, and demonstrating that mastery through a progressively more difficult sequence of oral examinations — a process which, on average, takes four years to complete, and for some, much longer than that. The guidebook issued to prospective cabbies by London Taxi and Private Hire (LTPH), which oversees the test, summarizes the task like this:

To achieve the required standard to be licensed as an “All London” taxi driver you will need a thorough knowledge, primarily, of the area within a six-mile radius of Charing Cross. You will need to know: all the streets; housing estates; parks and open spaces; government offices and departments; financial and commercial centres; diplomatic premises; town halls; registry offices; hospitals; places of worship; sports stadiums and leisure centres; airline offices; stations; hotels; clubs; theatres; cinemas; museums; art galleries; schools; colleges and universities; police stations and headquarters buildings; civil, criminal and coroner’s courts; prisons; and places of interest to tourists. In fact, anywhere a taxi passenger might ask to be taken.

If anything, this description understates the case. The six-mile radius from Charing Cross, the putative center-point of London marked by an equestrian statue of King Charles I, takes in some 25,000 streets. London cabbies need to know all of those streets, and how to drive them — the direction they run, which are one-way, which are dead ends, where to enter and exit traffic circles, and so on. But cabbies also need to know everything on the streets. Examiners may ask a would-be cabby to identify the location of any restaurant in London. Any pub, any shop, any landmark, no matter how small or obscure — all are fair game. Test-takers have been asked to name the whereabouts of flower stands, of laundromats, of commemorative plaques. One taxi driver told me that he was asked the location of a statue, just a foot tall, depicting two mice sharing a piece of cheese. It’s on the facade of a building in Philpot Lane, on the corner of Eastcheap, not far from London Bridge.

If you go to LTPH headquarters, where the examinations are conducted, you will behold a grim bureaucratic scene, not much different than the one you might find in an office devoted to tax audits: nervous test-takers, dressed in suits, shuffling into one-on-one sessions with stone-faced examiners. But for more than a century, since the first green badge was issued to a hackney cabman piloting a horse-drawn carriage, the test has been known by a name that carries a whiff of the occult: the Knowledge of London.


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Some trace the origins of the Knowledge to the Great Exhibition of 1851, when visitors to London complained about inept hackney carriage drivers.

Some trace the origins of the Knowledge to the Great Exhibition of 1851, when visitors to London complained about inept hackney carriage drivers.Credit Popperfoto/Getty Images


The origins of the Knowledge are unclear — lost in the murk of Victorian municipal history. Some trace the test’s creation to the Great Exhibition of 1851, when London’s Crystal Palace played host to hundreds of thousands of visitors. These tourists, the story goes, inundated the city with complaints about the ineptitude of its cabmen, prompting authorities to institute a more demanding licensing process. The tale may be apocryphal, but it is certain that the Knowledge was in place by 1884: City records for that year contain a reference to 1,931 applicants for the “examination as to the ‘knowledge’ [of]…principal streets and squares and public buildings.”

In 2014, in any case, the Knowledge is steeped in regimens and rituals that have been around as long as anyone can remember. Taxi-driver candidates — known as Knowledge boys and, increasingly today, Knowledge girls — are issued a copy of the so-called “Blue Book.” This guidebook contains a list of 320 “runs,” trips from Point A to Point B: Manor House Station to Gibson Square, Jubilee Gardens to Royal London Hospital, Dryburgh Road to Vicarage Crescent, etc. The candidate embarks on the Knowledge by making these runs — that is, by physically going to Manor House Station and finding the shortest route that can be legally driven to Gibson Square, and then doing the same thing 319 more times, for the other Blue Book runs.

But the Knowledge is not simply a matter of way-finding. The key is a process called “pointing,” studying the stuff on the streets: all those places “a taxi passenger might ask to be taken.” Knowledge boys have developed a system of pointing that some call “satelliting,” whereby the candidate travels in a quarter-mile radius around a run’s starting and finishing points, poking around, identifying landmarks, making notes. By this method, the theory goes, a Knowledge student can commit to memory not just the streets but the streetscape — the curve of the road, the pharmacy on the corner, the mice nibbling on cheese in the architrave.


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While studying for the Knowledge, aspiring taxi drivers practice runs by motorbike, with a map strapped to the windscreen.

While studying for the Knowledge, aspiring taxi drivers practice runs by motorbike, with a map strapped to the windscreen.Credit Bloomberg


Decades ago, most Knowledge boys did their runs on bicycles. Now, nearly all test-takers buy or lease motorbikes. In 2014, there are thousands of men and women plying the city’s streets on two wheels, at all hours, in all weather, doing runs and gathering points. It’s a ubiquitous London sight: a Knowledge boy on a bike, with a map or notepad strapped to his Plexiglas windscreen. When the candidate has completed his 320 Blue Book runs — and his accompanying 640 quarter-mile radii point-gathering expeditions — he will have covered the whole of central London. At which time he takes a brief written exam, proceeds to the first stage of the oral examination process, and the test begins in earnest.

The testing takes place at the LTPH office in a series of “appearances,” face-to-face encounters between Knowledge candidate and examiner. The test-taker is asked to “call a run”: to identify the location of two points and to fluidly recite the shortest route between the points, naming all the streets along the way. A Knowledge boy is first given 56 days between appearances to study; then, as he progresses, 28 days, and 21. The questions, meanwhile, get harder, with candidates asked to locate more obscure points and to recite longer, more byzantine journeys across London’s byways. Each appearance consists of four runs, and each run is scored according to an elaborate numerical system. Your total score earns you a letter grade, from AA to D. (AA’s are exceedingly rare; D’s aren’t.) Candidates who acquire too many bad grades are bumped backward — “red-lined” from appearances every 28 days back to every 56 days, or from 21s to 28s. There is no such thing as “failing” the Knowledge. You can either quit, or persevere and pass: proceed all the way through to the end of your 21-day appearances, gaining sufficient points to earn your “req” — to meet the “required standard,” and complete the test.

For Matt McCabe, that goal was within spitting distance. He was “on 21s, on six points,” making appearances just three weeks apart, with six points on his tally, and only six more needed — just two solid appearances, perhaps, away from getting his req. It was a pointing mission that brought McCabe to Fish Island that morning in January. He’d visited the neighborhood before, but had heard that a new point had come up in a candidate’s appearance a couple of days earlier. So he’d returned to take another look at the area — in particular, at H. Forman & Son, a wholesale fishmonger on Stour Road.


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McCabe on a “pointing” mission in Fish Island, an industrial district in East London.Credit Jody Rosen


“Forman’s is quite famous,” McCabe said. He was standing outside the H. Forman & Son warehouse, a shedlike structure the size of a small airplane hangar. “They supply fish to the top restaurants in London. But now they’ve opened their own restaurant.” McCabe scrutinized the menu posted on a wall outside the building. He took a note on a small pad: “Chef: Lloyd Hardwick.” Hardwick, McCabe discovered by checking Google, had been the executive chef at the sleek restaurant on the top floor of the Tate Modern museum. “You have to look into these things. You know, the examiner could turn around and say, ‘Name me two Angela Hartnett restaurants,’ or ‘Name me four Gordon Ramsay restaurants.’ ” McCabe showed me a sign indicating that the restaurant also housed an art gallery. “You’ve got to note that. Instead of Formans restaurant, the examiner might give you Forman’s Smokehouse Gallery. That could be enough to throw you off.”

McCabe said: “This is an up-and-coming area. It looks like nothing, you know — but you put a bit of paint on the brickworks, smarten the place up, and all of a sudden it becomes a spot for little boutique stores or the up-and-coming D.J.s. You’ve got warehouse conversions; you’ll see guys coming out of the buildings in the morning — suit-and-tie, briefcase. If you’re driving a cab, you could pick someone up in the City at the end of the day heading back this way.”

McCabe had spent his entire professional life in the building trade. He’d worked alongside his father, an electrical engineer, and then as the owner of his own small firm specializing in roof maintenance, steel work and asbestos removal. He liked the work, but it was grueling — 15 hours days, seven days a week — and the £50,000 ($80,000) he took home wasn’t enough, to his mind, to justify the sacrifices. A job as a taxi driver seemed an attractive alternative. London cabbies are self-employed businessmen who set their own schedules. The metered fares of taxis are high, and drivers keep what they earn. The overhead — the cost of gas and of owning or leasing a taxi — can be steep, but cabbies who put in the hours can make a good living. There are no official statistics, but drivers themselves will tell you that London cabbies can earn around £65,000 per year, about $100,000, while maintaining an enviably flexible schedule. As a cabby, McCabe figured, he could work seven, 10, 15 days straight — and then take four days off to spend time with his wife Katie, a hairdresser, and their children, Archie, 4, and Lulu, 3. He sold his engineering outfit and devoted himself full-time to the Knowledge, living off the savings he’d gained from the sale of his business.

It was now 37 months since he’d paid the £525 enrollment fee to sign on for the test and appearances. “The closer you get, the wearier you are, and the worse you want it,” McCabe said. “You’re carrying all this baggage. Your stress. Worrying about your savings.” McCabe said that he’d spent in excess of £200,000 on the Knowledge, if you factored in his loss of earnings from not working. “I want to be out working again before my kids are at the age where someone will ask: ‘What does your daddy do?’ Right now, they know me as Daddy who drives a motorbike and is always looking at a map. They don’t know me from my past, when I had a business and guys working for me. You want your life back.”

 

The Knowledge is a uniquely British institution: a democratization of what P. G. Wodehouse winkingly called the feudal spirit, putting an army of hyperefficient Jeeveses on the road, ready to be flagged down by any passing Bertie Wooster.

 

The Knowledge is notorious for snatching away lives, and for putting minds in a vise grip. “Everything becomes about the Knowledge,” McCabe said. “My wife will be talking to me about plans or the kids, and it’s not even registering what she’s saying. Because all I’m thinking is, ‘I can’t turn right into that road in Hammersmith, can I?’ If you read the paper, or watch the news or a film, you’re looking at the background. ‘Oh, I know that road there.’ ”

McCabe said that he dreamed about the Knowledge: sometimes exhilarating visions of zooming through London streets, more frequently nightmares about unfamiliar roads or disastrous LTPH appearances. Often, McCabe would wake in the middle of the night and hurry downstairs to study the map. In his dining room, there were three maps: two jumbo London street plans — one laminated on the dinner table and one tacked to the wall — and an enlarged view of the W1 postcode, the bustling zone which stretches south from Marylebone to Piccadilly and east to Soho. McCabe had ledgers he’d filled with jottings on topics like “Small and Awkward Squares.” There were also flashcards that McCabe had made up, listing a point on one side (“Tooting Mosque, SW17″) with information about its location and navigation on the other (“Gatton Road, one way, access via Fishponds Road”). McCabe stacked the cards in piles of 300; he had 40,000 in all. His home, he said, had become a library of the Knowledge.

 

McCabe had ledgers filled with jottings on topics like “Small and Awkward Squares,” and 40,000 flashcards.

 

But book-learning gets you only so far. “You’ve got to get out on the bike,” McCabe said. When he was doing Blue Book runs, McCabe would ride the streets all night, leaving when his wife got home from work at 9 p.m. and returning at 4 in the morning. Pointing, McCabe told me, can be “very cold, very lonely, very dangerous.” One night, McCabe was out pointing on his motorbike when a driver slammed into him from behind. McCabe went over the roof of the car, but suffered just a few scrapes and bruises. The bike was totaled. “I’m stationary in the filter lane, and the car just came around the bend and hit me,” McCabe said. “This was on a road called Pound Lane. Right across from the fire station at the corner of Harlesden Road.”

As McCabe progressed through the Knowledge, his pointing technique had become more refined. “At the beginning you might go to the Savoy Hotel on the Strand,” he said. “That’s a famous point; everyone knows it. But you start to think: What’s a more obscure point on the Strand? So you’ll pick up the Coal Hole Public House a few doors along. You start looking at George Court and find a little bar called Retro, a gay bar that plays ’80s music. You start thinking about the bits and pieces. I’m at the stage now where I’m looking at a new bar that just opened — inside a cinema. I’m picking up handbag shops, bowling alleys. You learn to kind of savor them little gems.”


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Taxis from the ’30s, ’60s and the present day.

Taxis from the ’30s, ’60s and the present day.Credit Clockwise from top left: E.F. Corcoran/Topical Press Agency, via Getty Images; Malcolm/Getty Images; Ben Stansall/Agence France-Presse – Getty Images


It is tempting to interpret the Knowledge as a uniquely British institution: an expression of the national passion for order and competence, and a democratization of what P. G. Wodehouse winkingly called the feudal spirit, putting an army of hyperefficient Jeeveses on the road, ready to be flagged down by any passing Bertie Wooster. But the Knowledge is less a product of the English character than of the torturous London landscape. To be in London is, at least half the time, to have no idea where the hell you are. Every London journey, even the most banal, holds the threat of taking an epic turn: The guy headed to the corner newsagent makes a left where he should have gone right, blunders into an unfamiliar road, and suddenly he is Odysseus adrift on the Acheron. The problem is one of both enormity and density. From the time that London first began to spread beyond the walls surrounding the Roman city, it kept sprawling outward, absorbing villages, enlarging the spider-web snarl of little roads, multiplying the maze. Take a look sometime at a London street map. What a mess: It is a preposterously complex tangle of veins and capillaries, the cardiovascular system of a monster.

All metropolises are quirky, but in most of them efforts have been made to mitigate the idiosyncrasies, to make the cities legible, navigable, beautiful. In Manhattan and Chicago, planners tamed chaos with gridded street schemes; Baron Haussmann obliterated twisty medieval Paris with his sweeping grands boulevards, transforming the city into a linked chain of vistas, plazas and parks. London, though, makes no sense. It was the capital city of the greatest empire in history, yet it doesn’t look or feel imperial. There are miles of monotonous ugliness, disrupted not by splendor, but by gentility — the pretty whitewashed homes and stately squares in the well-heeled districts of West and North London. St. Paul’s Cathedral sits at the back of a small semicircular plaza that is pinned-in by the office towers and bendy streets of the financial district. It is difficult to get a decent view of the most beautiful building in town.

The genius behind St. Paul’s, the architect Christopher Wren, nearly became London’s Haussmann. Just days after the catastrophic Great Fire of 1666, Wren produced a plan to rebuild London as an Italian-style city, with wide boulevards that terminated in piazzas and raised stone quays. But the plan never gained traction. The explanation usually given is economic: If Chicago is an expression of American pragmatism, and Paris an ode to symmetry, then London is a monument to English mercantilism and love of private property, to the power of the bourgeois freeholders and shopkeepers, who clung too tightly to their little patches of land to permit the clearing of space for Wren’s plan. In London, lucre trumps grandeur.

 

A London street map is a mess: a preposterously complex tangle of veins and capillaries, the cardiovascular system of a monster.

 

The result is a town that bewilders even its lifelong residents. Londoners, writes Peter Ackroyd, are “a population lost in [their] own city.” London’s labyrinthine roadways are a symbol — and, perhaps, a cause — of the fatalism that hangs like a pea-soup fog over the Londoner’s consciousness. Facing the dizzying infinitude of streets, your mind turns darkly to thoughts of finitude: to the time that is flying, the minutes you are running late for your doctor’s appointment, the hours ticking by, never to be retrieved, on the proverbial Big Clock, the one even bigger than Big Ben. You can see it every day in Primrose Hill and Clapham, in Golders Green and Kentish Town, in Deptford and Dalston. A nervous man, an anxious woman, scanning the horizon for a recognizable landmark, searching for a street sign, silently wondering “Where am I?” — a geographical question that grades gloomily into an existential one.

Which is where the Knowledge comes in. It is a weird city’s weird solution to the riddle of itself, a municipal training program whose graduates are both transit workers and Gnostics: chauffeurs taught by the government to know the unknowable.

If you follow your London A-Z Street Atlas halfway up Caledonian Road, in Islington, you’ll find Knowledge Point, the largest of London’s 10 schools dedicated to the test. The school occupies a nondescript two-story building, but you can’t miss it: At all hours of the day, Knowledge boys’ motorbikes line the sidewalk out front. For several years in the 1990s, there was something else parked alongside the bikes: the steed of a mounted Metropolitan Police officer, who did the Knowledge on horseback, after, and during, his working hours.

The school offers specialized lectures on dozens of topics: “Hotels Outside Central London,” “South West London Turnarounds,” “Barracks & Military Establishments,” “Lambeth & Waterloo.” Pupils pick up trade secrets, the aides-mémoires and acronyms that have been passed between generations of Knowledge boys. There’s “Cat Eats Well Then Shares Her Beef Gravy,” a mnemonic denoting a path north from the Aldwych — the crescent-shaped road that loops above the Strand — along a sequence of one-way streets: Catherine, Exeter, Wellington, Tavistock, Southampton, Henrietta, Bedford, Garrick. To access C.A.B. — the Chelsea, Albert, and Battersea bridges — you take C.O.B.: respectively, Chelsea Bridge Road, Oakley Street and Beaufort Street. A series of streets running north to south through Soho — Greek, Frith, Dean, Wardour — are Good For Dirty Women.

But the majority of a student’s time at Knowledge Point is spent in two cramped rooms on the school’s ground floor, where maps are arranged on flat tables and angled easels. These rooms are devoted to “calling-over”: sitting with a partner, taking turns reciting runs, in an effort to replicate the conditions of oral examinations at the LTPH office. Anytime you step into Knowledge Point you will find students, faces pinched in concentration, calling-over runs in the specialized jargon mandated by Knowledge examiners. A skilled caller — a “woosher,” in Knowledge slang — can sound like a slam poet or a rapper, whipping off street names and turnings in a pleasing syncopated rhythm as he races through London streets in his mind’s eye:Leave on the right Lillie Road, left Eardley Crescent, left Warwick Road, forward Holland Road, comply Holland Circus, leave by Uxbridge Road, forward and right Shepherd’s Bush Green. More often, what you will hear at Knowledge Point is the sound of strain: groans, hems and haws, cursing.


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At Knowledge Point School in Islington, candidates prepare for their oral exams by taking classes on topics like ‘‘South West London turnarounds,’’ reciting runs of streets with partners and learning aides-mémoires for London’s bridges.

At Knowledge Point School in Islington, candidates prepare for their oral exams by taking classes on topics like ‘‘South West London turnarounds,’’ reciting runs of streets with partners and learning aides-mémoires for London’s bridges.Credit Rory Van Millingen


Matt McCabe had been coming to Knowledge Point since he started on the test. A stickler for routine, he arrived each morning at 8:45. When the doors opened at 9, he would sit down across a table from his call-over partner, Steven Vine. I met McCabe and Vine at Knowledge Point one morning and watched them call-over. They spent hours switching off, settling into a patter of run-calling punctuated by mumbled expletives and other exclamations: “good pull” (when you correctly identify a tricky point), “bad drop” (when you forget a point or road that you should know), “nice line” (when your call sketches a nice straight path across the map).

To call-over effectively is to find a golden mean between geography and geometry. The aim is not just to navigate cleanly, naming the right roads, but to make the shortest and most elegant line between points. While McCabe called-over a run, Vine followed along, tracing his partner’s route with a marker on the laminated map. When McCabe finished, he and Vine stretched a ball-bearing chain over the map to assess the straightness of his call. This practice is known as “cottoning the run,” a phrase that dates to the days when Knowledge boys would use lengths of cotton twine to measure their runs. “They have a saying, ‘Don’t let the cotton strangle you,’ ” McCabe said. “It’s a reminder: Don’t get too tied up in having the perfect line. You’re always trying to calculate: ‘Which one would look the prettiest on the map?’ But sometimes you just gotta let it flow.”



The London landscape throws up constant impediments to the ideal of traveling in a straight line: parks, railway yards, one-way streets. The Thames presents another challenge. Because the area below the river is referred to as South London, most people assume that the dozen central London bridges spanning the water stretch north-to-south. In fact, the Thames’s flow is meandering; in places, the river crossings run along the opposite axis. (A Knowledge boy mnemonic instructs: “East to West, Lambeth or Westminster Bridge is best.”) At Knowledge Point, McCabe leaned over the map and pointed to the King’s Road in Chelsea. “If you were going from here, say, all the way out to Canary Wharf, you might cross the river twice to make it the shortest line. So you might run it across Westminster Bridge and bring yourself back across Tower Bridge. That will be a straight line, because you’re understanding the bends in the river.”

At his late stage of the test process, McCabe found himself facing a novel problem: too much Knowledge. “London now feels very small. At the beginning, you would be standing in Piccadilly and someone says to you, ‘Take me to Kilburn,’ and you would say: ‘Oh my God, that feels miles away.’ Now, I can take you endless amounts of ways. And that’s the dilemma you’ve got now: you see too many options.”

Seeing, for a Knowledge candidate, is everything — at its heart, the Knowledge is an elaborate exercise in visualization. When McCabe called-over, he closed his eyes and toggled between views: picturing the city at street level, the roads rolling out in front of him as if in a movie, then pulling the camera back to take in the bird’s eye perspective, scanning the London map. Knowledge boys speak of a Eureka moment when, after months or years of doggedly assembling the London puzzle, the fuzziness recedes and the city snaps into focus, the great morass of streets suddenly appearing as an intelligible whole. McCabe was startled not just by that macroview, but by the minute details he was able to retain. “I can pull a tiny little art studio just from the color of the door, and where it’s got a lamppost outside. Your brain just remembers silly things, you know?”

 

The posterior hippocampus, known to be important for memory, is bigger in London taxi drivers than in most people and, for successful Knowledge candidates, enlarges as the test progresses.

 

The brains of London taxi drivers have attracted scholarly attention. Eleanor Maguire, a neuroscientist at University College London, has spent 15 years studying cabbies and Knowledge boys. She has discovered that the posterior hippocampus, the area of the brain known to be important for memory, is bigger in London taxi drivers than in most people, and that a successful Knowledge candidate’s posterior hippocampus enlarges as he progresses through the test. Maguire’s work demonstrates that the brain is capable of structural change even in adulthood. The studies also provide a scientific explanation for the experiences of Knowledge students, the majority of whom have never pursued hi