Private detectives from all over the UK descend on York on Saturday for their annual meeting. But they're such an unassuming bunch you probably won't even notice they're here, says STEPHEN LEWIS.

THINK of a private detective and who springs to mind? Nondescript man in a tan raincoat, sitting in a beat-up saloon with a fedora tipped over his eyes and a cigarette dangling from his lips? Feisty, ass-kicking woman with a don't-mess-with-me attitude and a wealth of one-liners? Effete Victorian aristocrat with a deerstalker hat, meerschaum pipe and giant magnifying glass?

Wrong every time. Philip Marlowe, VI Warshawski and Sherlock Holmes may have helped form our idea of what a private investigator is like. But the true private eye has one ability above all: that of being able to blend into the background. Oozing charisma is the last thing they need.

So just what will the 50-or-so private investigators descending on York's Novotel for their annual conference on Saturday look like?

I asked a real-life York gumshoe.

In typical cloak-and-dagger fashion, the man from Insight Investigations didn't want his real name using - but he didn't mind talking. There probably won't be a single mac or trilby hat in sight at the Novotel on Saturday, he said. They are more likely to be ordinary-looking middle-aged gents in business suits, and a few younger in chinos and smart-casual wear.

Not that he has got anything against hats. If you're on a surveillance job that involves following someone, they come in very handy.

"If you're wearing a hat, and have the option of taking it off, it changes your profile," 'Eddie' said. Reversible jackets are also good: anything that alters your appearance enough to make you difficult to spot.

The lives of fictional private detectives tend to be action-packed, dangerous and full of incident. Not so their real-life counterparts.

"It is not at all glamorous," Eddie admitted. "I wish it was!" One of the main qualities a private investigator needed was patience, he said. That came in useful if you were following someone and they ended up lying in bed until 2pm. "You have to be able to stick with it and not switch off," he said.

Former police inspector-turned private investigator David Farrar agreed the life wasn't exactly full of thrills and spills.

Much of the work involves serving injunctions on people - usually people who don't want to have them served. So there is always a risk, David said, of finding yourself being chased down the garden path by a man who had just been served. But exciting?

"It's very boring work, on your own!" he said. "It sometimes involves very long, unsociable hours." That's because very often the people you need to speak to aren't conveniently at home during the day. The only time you might be able to find them is at weekends or late in the evenings.

Not a job for nine-to-fivers who like to spend their evenings slumped in front of the TV, in other words.

So what makes a good private detective? Not being tall, charismatic, attractive and snappily-dressed, that's for sure - all the qualities that mark out the fictional detectives. The real-life gumshoe's most prized ability is to remain un-noticed. To be, in fact, a little grey.

According to Eddie, a former Army man, the kind of work private investigators tend to get these days falls into three categories. There's commercial work - investigating insurance claims, say, or process-serving or doing work on fraud cases for solicitors. There's industrial work - being taken on by companies who think a member of staff may be stealing or fiddling the books, for example. And there is 'public' work: divorce cases or missing persons' inquiries.

The general rules of thumb for a good private detective, Eddie said, are to be able to blend in, to act normally and be discreet. There is one golden rule that comes above all others. Wherever the private detective's work takes him, he must have a convincing reason for being there.

Occasionally, the job can be exciting. He once worked undercover at a furniture warehouse where managers believed staff were stealing flatpack kitchen units. He got a job at the factory and began sniffing around. He tried dangling a few fishhooks. "I tried approaching some of the staff and saying 'I've just moved into a house, do you know if the company sells cheap kitchens?'" he said. No one took the bait. Eventually he worked out the problems were occurring on the night shift. He switched to night work, then got a couple of fellow investigators to tail a delivery lorry whose driver he suspected. They did so, with a video camera, and clocked him dropping off a kitchen unit at an address he had no business visiting. Case solved.

Undercover work is exciting, but it doesn't come round that often, says Eddie. Much of the rest of the job is routine and uninteresting.

So why do people become private investigators? Often, according to Roger Bunting, chairman of the Institute of Professional Investigators, which is organising Saturday's conference, private detectives are former police or military men who want to make use of the skills they have learned in their earlier careers.

They tend to have certain character traits, he added. They are usually inquisitive and don't necessarily believe everything they are told; they can be a bit anti-authoritarian, with a rebellious streak; and they need to be very analytical. "You've got to be able to listen to what you're told, and you've got to be able to spot what are lies," he said. "Con men will look you in the face and tell you the most blatant untruths."

So how do you tell when you're being lied to? "You go on what you know, what is probable, what the evidence is," said Mr Bunting.

According to Eddie, women make particularly good private detectives because they are inquisitive. They are also useful to have around if you are tailing someone and want to remain unnoticed. You can pose as a couple going for a meal or a drink. "And it looks very natural."

So what will the nation's private eyes, men and women, be talking about on Saturday?

Partly, Mr Bunting said it will be a chance to do some networking.

It is always useful for an investigator to know others working in other parts of the country in case they need someone there they can trust.

Partly it will be a chance to look at the latest technology - surveillance equipment, cameras and the like. But the main topic will be the forthcoming regulation of the investigation industry. From next year, all 110,000 or so private investigators working in the UK will have to be licenced - and it will involve them being regulated, the way doormen and private security firms are.

It will mean a series of rigorous standards being set to govern their work - and possibly even an NVQ-style qualification.

Sorry? You mean private eyes will have to sit exams? It's not unusual, apparently. 'Eddie' himself has a diploma in private investigation.

Even David Farrar, despite 30-odd years as a copper, had to pass "quite a rigorous test" before he was accepted for membership of the Association of British Investigators. Philip Marlowe would be turning in his grave.

The private eye's CV

What does it take to make a great private detective? This is how their CV may look:

Previous career: police or armed forces

Skills: blending in/ good interviewer/ strong analytical skills

Distinguishing physical characteristics: none

Fashion sense: business suits/chinos/smart casual dress

Other interests: loitering inconspicuously/ watching people through zoom lenses/ drinking cold coffee out of polystyrene cups/interest in hi-tech electronic surveillance equipment

Great fictional private eyes

Sherlock Holmes: Who else? Sir Arthur Conan Doyle almost invented the crime novel and Holmes remains, intellectually, the finest detective of them all, says Roger Bunting

Hercule Poirot: Belgian, portly and quite often pretty annoying: but a great detective's brain

Miss Marple: Few investigators have ever been less conspicuous than the little old lady next door - which means she'd probably make a great modern private eye

Sam Spade: Dashiell Hammet's private investigator was the best of all, according to local crime writer John Baker, creator of York-based private detective Sam Turner. Hammet was a private investigator, so he really knew what he was writing about.

Philip Marlowe: The great Raymond Chandler's finest creation, a tough, hard-boiled private eye with a soft centre, made immortal by Humphrey Bogart

Jim Rockford: James Garner's character in US TV series the Rockford Files was likeable, fun, knockabout, and always in trouble

Shoestring: Trevor Eve's Bristol-based TV gumshoe was low-key, oddly vulnerable - and massively popular

VI Warshawski: The divorced, hard-boiled, wise-cracking and fearless Chicago investigator created by writer Sara Paretsky set the standard for fictional female private eyes

Columbo: OK, so strictly-speaking the famously crumpled Los Angeles homicide detective was a policeman, not a private investigator. But he had all the hallmarks of the classic PI, insists Roger Bunting. "Nobody takes any notice of him, he looks an idiot - but his brain is working all the time."

Updated: 11:16 Wednesday, September 07, 2005