A very odd crime unit

London peculiar: Christopher Fowler explains how he created his curmudgeonly detective duo, Bryant & May

I have never met an author who did not read voraciously as a child. Quantity has little to do with quality, though, and parents always worry that their children read trash. While my mother perversely pushed George Bernard Shaw at me, I collected every issue of Famous Monsters of Filmland. After devouring the articles, I sent away for giant weather balloons, sea monkeys, 8mm reels of The Giant Claw, Aurora model kits and the Baby Chick Incubator. My mother said I couldn't send off for a monkey because if the overseas postage was short it would arrive dead.

The side-effect of reading trash is that it leads you, by a process of osmosis, to literature. Because Famous Monsters magazine talked endlessly of Dracula it was necessary to read Bram Stoker, which led to Wilkie Collins, Conan Doyle and Edgar Allen Poe. From an interest in horror and the supernatural came a fascination with reading murder mysteries, and eventually writing them.

To invent your own detective, it's necessary to glance at the sleuths of the past. When Sir Arthur Conan Doyle conceived Sherlock Holmes, why didn't he give the famous consulting detective a few more quirks: a wooden leg, say, and an Oedipus complex? Well, Holmes didn't need many physical tics or personality disorders; the very concept of a consulting detective was still fresh and original in 1887.

Things are different now. Thanks to TV's incarnation of the melancholic Morse, present-day gumshoes are often more interesting than the crimes they solve. They're certainly more varied, from Mark Haddon's autistic boy sleuth in The Curious Incident of the Dog in the Night-Time, to Michael Dibdin's Aurelio Zen, who negotiates his way through the corrupt corridors of the Italian police system. John Burdett has created a Buddhist cop who ponders life and death in Thailand, and Jason Goodwin has given us a wise eunuch who investigates crimes in old Istanbul. There's a long line of exotic detective fiction that's particularly appealing to British readers. Now, though, the field is crowded. There are cats and dogs that solve crimes, and Leonie Swann has even come up with a sheep that unravels the murder of its farmer, although it has a habit of drifting off at crucial moments.

English authors got off to a rocky start with characters like Sexton Blake and Raffles, who were so chinless you have to wonder how they managed to put a pillow-case on by themselves. The queen of crime, Agatha Christie, was always more concerned about the clockwork cleverness of the plot, never the investigator. Attempts to invest Hercule Poirot (let alone her paper-thin sleuths Tommy and Tuppence Beresford) with interesting characteristics have always been doomed, although Margaret Rutherford stamped Miss Marple with her own brand of chin-wobbling bluster.

So how does a writer create a memorable detective these days? I started out with a matchbox that read "Bryant & May - England's Glory". The label gave me their names, their nationality, and something altogether more vague and appealing, the sense of a national institution with roots in London's sooty, dimly-lit past. My detectives, I decided, would be old, troublesome, wayward and faintly disreputable. Broadly speaking, there are two approaches to crime: the realistically detailed police procedural, usually grim and downbeat, and the more left-field, joyous theatre of ideas in which past masters once specialised. Knowing that I would never be able to handle the former, I set about reviving the latter. I grew up in Greenwich, part of London transformed by lousy planning and tourism, and practically lived in East Greenwich library, which now lurks beneath a motorway and is barely used, but it was where I discovered Dickens, Woolf, Waugh, Wodehouse, Ballard, Peake, H H Munroe and M R James. I noticed that these writers heightened realism to a frequently surreal level and, if I couldn't follow in their footsteps, I might at least tiptoe tentatively behind them.

I decided that London would be the third character; not the tourist city of guidebooks but the peculiar London of invisible societies, hidden parks and drunken theatricals, the people and places I show to friends when they visit. Everyone remembers Soho's Coach & Horses for its rude landlord Norman Balon, but fewer realise that it's the drinking hole of the Prince Edward's scenery shifters. One evening, I overheard a tattooed bruiser at the bar telling his mate, "I says to 'im, call yourself a bleeding Polonius? I could shit better speeches to Laertes than that." Write such dialogue down and you follow authors like Firbank and Orton, who became fascinated by London's magpie language and behaviour.

By making Bryant & May elderly, I could make them simultaneously behave like experienced adults and immature children. Bryant, I knew, came from Whitechapel, was tortoise-like, scarf-wrapped, esoteric, eccentric, bad-tempered and myopic. He would wear a hearing aid and false teeth, and use a walking stick. John May was born in Vauxhall, was taller, fitter, more charming, friendlier. Every night, the detectives would walk across Waterloo Bridge and share ideas, because a city's skyline is best sensed along the edges of its river, and London's has changed dramatically in less than a decade, with the great ferris wheel of the London Eye lending a raffish fairground feel to a traditionally conservative area.

The hardest part was accepting the fact that, after publishing 20 books, I was once again a first-timer. I had to start relearning everything from scratch. Smart plotting was not enough; situations needed to be generated by character. The easiest part was, oddly, being placed within a set of rigid rules; authors secretly love the imposition of restrictions. I stuck by my character outlines, even though a radio interviewer told me I should have made everyone younger, which would allow for more sex and violence - the very thing I did not wish to do. It wasn't a matter of prudery; rather the fact that a sexual bout or a fist fight is too lazy an exit from an awkward scene.

It's hard enough keeping track of your story through one novel, let alone a series, but I decided to link six free-standing Bryant & May novels with compounding clues and recurring characters as reward-points for loyal readers. I realised I'd become an obsessive when I wallpapered the entire lounge, including the windows, with Post-It notes. I had no love life. Friends stopped calling. Even the cat went to live somewhere else. I still held down a day job but would come home exhausted, turn on the computer, thumb through my clippings and paper scraps bearing scribbled ideas, and try to remember where on earth I was up to.

Then something odd happened. The writing got easier. My characters took flight, and plots became more organic. I finally trusted in Bryant & May as much as my readers, who had been writing to me with ideas and leaving messages on my website. Bryant & May starting misbehaving, and the less predictable they were the more the stories came to life.

As a location, London offers more anachronistic juxtapositions than most European cities - you're likely to find a church on the site of a brothel - and it was important to find a way of reflecting this in the novels. The structure and geography of European streets are designed for the boulevardiers of vanished empires, but London continually reinvents. Feeling sure that Bryant could use its past to help him solve crimes, I created a police division, the Peculiar Crimes Unit, loosely based on one of the experimental units founded by the government during the Second World War, and added younger staff members who would be knowledgeable about the "new" London. Then I started trawling city streets for clues to puzzles. The Queen's Larder pub in Holborn is built over the basement where George III was temporarily cured of madness; I filed the fact. The Palace Theatre has steam engines powered by a tributary of the River Fleet; I made a note. London's railings sport acorns because they were a Roman symbol of hospitality; I jotted that down, too. I listened to oral histories of Londoners stored in museums, and ploughed through the diaries, notebooks and memorabilia hoarded by their families. These oddities provided just the sort of colourful sidebars Bryant could drag into his conversations, and as people tend to forgive the elderly when they digress, I was able to use them in the service of the plot.

Having finished the groundwork, I embarked on the actual writing. A friend from New York hoped I would adopt the style of Victorian novels. She lamented the passing of London's alleyway curiosities, but had an idealised notion of fogbound streets that has taken us generations to shake off. I told her I believed the core of modern London to be as quirky as ever, and set out to prove my point. The back-rooms of pubs, for example, still house all manner of peculiar club meetings. I recently spent an evening with the Dracula Society (not to be confused with the Vampire Society; they're still not on speaking terms) in a Paddington theatre pub where glass-rinsing barmaids joined in arguments concerning Darwinism versus the role of "intelligent design" in vampiric evolution. They knew that tomorrow night their views would be canvassed by another arcane gathering, the Fantasy Writers Group, perhaps, or the Tony Hancock Fan Club. Old West End bars like Gerry's, Eileen's, the Troy and the Colony were filled with self-conscious eccentrics. The ones I've found since are the real thing, packed with impassioned people who don't believe they are in any way strange.

In the search for original plots, I decided to produce a modern take on each type of "classic" crime in turn, from the locked-room mystery to the whodunnit. The unlikeliest elements of these tales turned out to be mined from London's forgotten lore; tales of lost paintings, demonised celebrities, buried sacrifices, mysterious guilds and social panics had casts of whores, mountebanks, lunatics and impresarios who have been washed aside by the tide of history, but now their descendants seem to be all around us. With such rich storylines to tap into, the problem is not one of finding cases for Bryant and May to investigate, but of choosing between them.

Did I succeed in creating memorable detectives? Only time will tell. But if having fun while unlocking knowledge is any sign of accomplishment, I guess the Bryant & May files will remain open for some time yet.

To order a copy of Christopher Fowler's fourth Bryant & May mystery, 'Ten Second Staircase', (Doubleday £12.99) for £11.50 (free p&p), call Independent Books Direct on 08700 798 897