After staking out private detectives for two years, Martin Gill and Jerry Hart have returned safely to Leicester University's Scarman Centre.
They believe that they are the first academics to dip their toes into the world of today's Philip Marlowes and Sam Spades. Unsurprisingly, they found that "research" was a dirty word among snoops. They were often greeted with suspicion and were accused of working for the Government or for rival agencies.
Of 1,700 questionnaires sent out to agencies and individual detectives, only 206 were returned. But these allowed the researchers a glimpse of this undercover world. They followed the questionnaires up with informal interviews, studies of business papers and studies of detectives at work.
Marlowe and Spade would recognise some aspects of the world recorded by Gill and Hart -it is suspicious, very male-dominated and filled with enthusiastic small-time operators. The survey found that about 80 per cent of PIs are ex-police.
But there the stereotype falls down. The world of private detection turns out to be nothing like as shady or exciting as Raymond Chandler and Dashell Hammett would have us believe.
Trouble rarely walks through the door these days with tales of murder and revenge. It is more likely to come in the form of lists of insurance fraudsters and debt defaulters: even the marital cases tend to centre on financial matters. The role of detectives in conducting manhunts armed with bills and writs makes them indispensable to businesses, if unglamorous.
It also makes them largely legal. "There are clearly a few out-and-out charlatans and criminals, but the majority are honest," says Mr Hart. "Although the private detective exists in a legislative grey area - he has no more statutory powers than you or me - he often has to use overt means so that his work can be presented in court. A significant proportion of the work centres on the courts or on industrial tribunals."
But he admits that as university researchers he and Dr Gill were never able to use underhand means and go about posing as prospective clients, for example. This necessity to be overt in the land of the covert possibly prevented them finding out detectives' darkest secrets.
And he agrees that there are pressures to be illegal: "They are under a great deal of pressure to take shortcuts that infringe legislation, for instance by tracing car registration numbers or finding out ex-directory phone numbers."
The Criminal Justice Act threatens to cut even this rather unracy element from the lives of detectives. Under the terms of the 1984 Data Protection Act, they could glean information over the phone by pretending to have legitimate access to the information. The Criminal Justice Act effectively closed this loophole.
Private detectives could take a further knock if they find themselves affected by legislation to prevent stalking. Private detectives are to petition the Home Secretary regarding the threat posed to their professional stalking activities.