This puzzle is inspired by "The Knowledge", the course of study required to become a licensed driver of a London "black cab". For over a hundred years, job candidates known as "Knowledge boys" or "Knowledge girls" have had to pass a sequence of oral exams in which they are given a pair of landmarks ("points") within a six-mile radius of Charing Cross and must recite a route that leads from one point to the other -- immediately, from memory, and in formal jargon.
(This New York Times Magazine article is a great introduction, and the first two minutes of the Modern Times "Streetwise" documentary from 1996 capture the flavor.)
Compared to the actual Knowledge, this puzzle is simple: The images at the top represent twelve passengers and their destinations. Each passenger's journey begins at home (a former home, that is), but fortunately the passengers are all quite well known, so their homes have been memorialized by blue plaques; Open Plaques catalogues their exact locations. And most of their destinations are well-known points of interest which any cabbie would be expected to know.
At the bottom are twelve sets of directions, written in symbols:
- Common Knowledge jargon phrases (such as "forward", "left", "comply", "leave by", "leave on the right", and "set down on the right") are each replaced by a symbol.
- Every remaining word in the directions is also replaced by a symbol. Question marks are wildcards which may stand for any word, but each other symbol translates to a specific word, and every use of that word is replaced by its symbol.
Here are the twelve cab journeys:
 Cetshwayo, King of the Zulus |
 From 18 Melbury Road, Kensington (12' 8" W) (2) to the statue of Nelson Mandela in Parliament Square (2) |
leave on the right Melbury Road, left Kensington High Street, forward Kensington Road, forward Knightsbridge, forward Piccadilly, right Duke of Wellington Place, left Constitution Hill, forward Spur Road, left Birdcage Walk, forward Great George Street, comply Parliament Square, set down on the right. |
GEORGE | R |
 Dame Agatha Christie, detective novelist and playwright |
 From 58 Sheffield Terrace (11' 50" W) (1) to to St Martin's Theatre where her play The Mousetrap is still running (4) |
leave on the left Sheffield Terrace, right Kensington Church Street, left Kensington High Street, forward Kensington Road, forward Knightsbridge, forward Piccadilly, forward Shaftesbury Avenue, right Monmouth Street, comply Seven Dials, leave by Mercer Street, left Shaftesbury Avenue, left West Street, set down on the left. |
MERCER | E |
 Dr. Samuel Johnson, author |
 From 17 Gough Square (6' 29" W) (3) to St John's Gate, where he held a job as a writer for the Gentlemen's Magazine (2) |
leave on the left Gough Square, left Pemberton Row, forward and right West Harding Street, right Fetter Lane, forward New Fetter Lane, forward and right Charterhouse Street, left St John Street, left St John's Lane, set down on the right. |
HARDING | I |
 Fred Russell, ventriloquist |
 From 71 Kenilworth Court, Lower Richmond Road, Putney (12' 55" W) (1) to the "dummy house" on Leinster Gardens (3) |
leave on the right Lower Richmond Road, left Putney Bridge Approach, forward Putney Bridge, forward Putney Bridge Approach, forward Fulham High Street, forward and left Fulham Palace Road, forward Talgarth Road, forward Queen Caroline Street, left Hammersmith Broadway, forward Shepherd's Bush Road, forward Shepherd's Bush Green, right Uxbridge Road, comply roundabout, leave by Holland Park Avenue, forward Notting Hill Gate, forward Bayswater Road, left Lancaster Gate, left Lancaster Gate, right Leinster Terrace, forward Leinster Gardens, set down on the left. |
BAYSWATER | S |
 John Lennon, musician |
 From 34 Montagu Square (9' 36" W)(5) to the Abbey Road Studios(2) |
leave on the left Montagu Square, forward Upper Montagu Street, left York Street, right Seymour Place, forward Lisson Grove, forward Grove End Road, forward Abbey Road, set down on the left. |
SEYMOUR | R |
 I.K. Brunel, civil engineer |
 From 98 Cheyne Walk (10' 28" W) (5) to the launch ramp of the Great Eastern (2) |
leave on the left Cheyne Walk, forward Chelsea Embankment, forward Grosvenor Road, right Vauxhall Bridge, forward Bridgefoot, forward Kennington Lane, forward Newington Butts, comply Elephant and Castle, leave by New Kent Road, comply Bricklayers Arms, leave by Tower Bridge Road, forward Tower Bridge Approach, forward Mansell Street, left Shorter Street, left Tower Hill, forward East Smithfield, forward The Highway, forward Limehouse Link, right Westferry Road, comply Westferry Circus, leave by Westferry Road, comply Marsh Wall Roundabout, leave by Westferry Road, right Napier Avenue, set down on the left. |
LIMEHOUSE | U |
 Mahatma Gandhi, law student |
 From 20 Baron's Court Road (12' 31" W) (1) to the Inner Temple where he studied law (0) |
leave on the left Baron's Court Road, right Challoner Street, left Castletown Road, left North End Road, left Gunterstone Road, right Trevanion Road, right Edith Road, right North End Road, left West Cromwell Road, forward Cromwell Road, forward Cromwell Gardens, forward Thurloe Place, forward Brompton Road, forward and right Knightsbridge, forward Piccadilly, right Duke of Wellington Place, left Constitution Hill, left The Mall, comply Charing Cross, leave by Trafalgar Square, right Duncannon Street, forward Strand, forward Aldwych, forward and left Strand, forward Fleet Street, right Bouverie Street, right Tudor Street, set down on the left. |
TUDOR | T |
 Marie Lloyd, music hall artiste |
 From 55 Graham Road (3' 57" W) (2) to the Theatre Royal where she often performed (6) |
leave on the right Graham Road, forward Dalston Lane, forward Balls Pond Road, left Essex Road, forward Islington Green, forward and left Upper Street, forward Islington High Street, forward St. John Street, right Rosebery Avenue, left Farringdon Road, forward Farringdon Street, right Fleet Street, forward Strand, right Aldwych, left Catherine Street, set down on the right. |
CATHERINE | N |
 Rosalind Franklin, crystallographer |
 From Donovan Court, Drayton Gardens (10' 45" W) (2) to Birkbeck College where she ran her research team (0) |
Leave on the left Drayton Gardens, left Fulham Road, forward Brompton Road, right Brompton Road, forward and right Knightsbridge, forward Piccadilly, forward Shaftesbury Avenue, left Charing Cross Road, forward Tottenham Court Road, right Store Street, forward Keppel Street, left Malet Street, set down on the right. |
STORE | T |
 Sir Learie Constantine, statesman and cricketer |
 From 101 Lexham Gardens (11' 42" W) (3) to Lord's Cricket Ground (3) |
leave on the right Lexham Gardens, left Marloes Road, forward Cheniston Gardens, forward and right Cheniston Gardens, left Wrights Lane, left Kensington High Street, right Campden Hill Road, right Notting Hill Gate, left Pembridge Road, comply roundabout, leave by Pembridge Road, forward Pembridge Villas, right Westbourne Grove, forward Bishop's Bridge Road, left Harrow Road, forward Harrow Road, forward and right Harrow Road, forward and left Harrow Road, left Warwick Ave, comply roundabout, leave by Clifton Gardens, forward Clifton Road, right Maida Vale, left St. John's Wood Road, set down on the left. |
CAMPDEN | E |
 Sir Robert Peel, Prime Minister |
 From 16 Upper Grosvenor Street (9' 18" W) (1) to old Scotland Yard, HQ of the Metropolitan Police which he founded (0) |
leave on the right Upper Grosvenor Street, left Park Lane, left Mount Street, forward and right Mount Street, right Berkeley Square, comply Berkeley Square, leave by Bruton Street, forward Conduit Street, right Savile Row, left New Burlington Street, right Regent Street, forward Coventry Street, right Haymarket, left Pall Mall East, forward Trafalgar Square, comply Charing Cross, leave by Whitehall, left Whitehall Place, set down on the left. |
COVENTRY | C |
 Wing Commander F.F.E. Yeo-Thomas G.C., secret agent |
 From Queen Court, Guilford Street (7' 22" W) (4) to the former location of Special Operations Executive HQ (5) |
leave on the left Guilford Street, right Russell Square, forward Woburn Place, forward Tavistock Square, left Endsleigh Place, right Endsleigh Street, left Endsleigh Gardens, forward Gower Place, left Gower Street, right Torrington Place, right Tottenham Court Road, left Howland Street, forward New Cavendish Street, right Marylebone High Street, left Paddington Street, left Baker Street, set down on the left. |
CAVENDISH | H |
For each passenger, take the number in the blue circle on their photo. Add it to the number on their destination's photo. Use the result to index into the name of the street along their route which is represented by the red question mark. Plot the results on the map at the location of each passenger's blue plaque and read from east to west to obtain the answer, STREET URCHIN.
