THE BROADER PICTURE; Closely observed trains

JEROME K. Jerome, Brookside, Beethoven, Mappa Mundi, Axe Edge, Black Douglas, Vulcan Enterprise, Bolton Wanderer, Lady Godiva and Emile Zola: the entries in trainspotters' notebooks form an eccentric litany, a locomotives' bible. "Our friends take the piss, but we don't care," said a 17-year-old who had travelled up from Exeter in his half-term holidays to stand on a railway bridge in Cardiff. Note the "we don't care" - the trainspotter as underdog, the teenage rebel clued into a secret world, defiant and misunderstood.

Trainspotters inspire anoraknophobia: their image is one of sad, sexless, anoraked middle-aged men, obsessive collectors dripping with cameras, binoculars, tape-recorders and notebooks; or of snotty-nosed schoolboys in short trousers and half-mast socks. But, for those smitten, the appeal endures from the ages of two to 92. So what's the fascination?

Maybe it's something to do with the names. Investigation reveals a microcosm of British life. Economists and evangelists (Adam Smith, William Booth), philanthropists and physicists (Thomas Barnardo, Robert Boyle), scientists and surgeons (Charles Darwin, Joseph Lister): they have all had locomotives named after them. There are even a couple of politicians (David Lloyd George and Winston Churchill). The professions are well represented, which is more than can be said of the monarchy: Queen Elizabeth II, the Queen Mother (often spotted in a siding in front of King's Cross gasworks), the Duke and Duchess of York and Lady Diana Spencer (she pulls mail trains and mobile post offices and is painted a regal maroon); these represent the sum total. No Prince of Wales, no Princess Royal, no Edward. But there is - swashbucklingly - a Black Prince and a Pegasus, as well as - less thrillingly - a Starlight Express. Over a dozen are named after newspapers and another dozen after TV and radio programmes (the BBC comes out on top). Recently, Lloyd's List 250th Anniversary - or, more correctly, 86222 Lloyd's List 250th Anniversary - was renamed Clothes Show Live.

The Royal London Society for the Blind (No 47745) now has its name-plates duplicated in Braille, at shoulder height. And Guide Dog pulls expresses out of King's Cross, while what was SS Great Britain is now known as Victim Support. Many more locomotives, though, are called after romantic-sounding places: Wild Boar Fell, Langdale Pikes, Shining Tor and Roseberry Topping, although there is an equal fascination with the mundane: Wigan Pier, Willesden Yard, Finsbury Park.

To hardcore trainspotters, however, the poetry, irony or general significance of a name is not really important. To them, numbers are all. Details of lowly shunters or anonymous "sprinters" (commuter coaches with a door on the front) are apparently as collectable as those of chunky freight locomotives or sleek, high-speed Eurostar expresses. But as one middle-aged chap in an anorak explained, "It never leaves you. It just changes as time goes on. The engines don't last forever - it's interesting to monitor which scrapyard they end up in." His wife was waiting in their car, reading a magazine; another train-spotting widow oblivious to her husband's anticipation that he might see Halley's Comet, or Robin Hood, or just good old 08806. Women, in fact, fare badly in the trainspotters' world. Out of more than 600 named locomotives in Britain, they barely rate double figures.

It was 1825 when Stephenson's "Locomotion" was first spotted travelling between Stockton and Darlington. A hundred and seventy years later, it's more likely to be a locomotive named after a closed coal mine; the ghost trains of the Nineties. Back in Cardiff, the 17-year-old on the railway bridge spots a locomotive called Driver John Elliot.Why the name? "Oh," he says, "a couple of years ago he stuck his head out of the cab window and was decapitated. Nobody wanted to drive that train after that, so they sent it up north and named this one after him, instead." !