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Any job, stripped to its bare essentials, is distressingly easy to fake. There are plenty of pseudo-doctors who've deceived the punters without attending so much as a night class in wrist-splinting. The British record goes to a Bradford man who impersonated a GP for 30 years. True, he was prescribing shampoo for conjunctivitis and creosote for a sore throat, but his patients didn't complain, and had he not been shopped by a member of his family he could still be practising. A few of the local pharmacists were suspicious, but when the creosote sales are going so well, you don't like to cause a fuss.

Dr Bogus (not his real name) hailed from Pakistan, where he'd worked as an unqualified chemist treating common ailments with his own remedies, such as Day Creosote and Night Creosote. He fooled the GMC, as many others have, with a fake medical degree and reference. Other bogus doctors have bypassed the GMC by forging its certificate of registration. In one celebrated case, a dyslexic man typed his own certificate, Tipp-Exed out all the mistakes and corrected them in biro.

Many of the hundred or so dud docs known to have tricked us since 1936 have, or have concocted, non-British backgrounds. They also tend to start as locums in hospitals which are desperately short of junior staff (ie all of them). When I did locums between 1991 and 1993, I'd just stroll on to the ward and head straight for the Milk Tray. No one ever checked my credentials; for all they knew I could have been a journalist desperate for material for my hugely successful bogus medical column.

General practice is well suited to the fraudster, as GPs tend to practise alone and can resist all attempts by others to scrutinise their work. In hospital, you might expect the loony locum to be put on the spot by his consultant on the first ward round, but many survive for months. Undergraduate medical education is so poor that consultants have low expectations of their junior staff. Indeed, some hoodwinked consultants have later admitted that the bogus house officers were by no means the worst they'd had. "Don't they teach you anything at medical school these days?" "No sir ..." "Jolly good. Carry on."

The GMC has now lightened up on the registration of doctors; photocopied certificates or anything with Tipp-Ex on are now rejected, and all hospitals are advised to check with GMC before employing any doctor. Fakes are on the wane, but they have at least taught us that front-line medicine is not nearly as academic as we'd like to think it is, and many people who wouldn't survive the brain torture of medical school would make perfectly good doctors. That said, most patients would rather have a competent tosser than an incompetent carer, so how do you tell if your doctor's a fake? Well, 96 per cent of fakes are men, so if a woman tells you she's a doctor, she probably is. For a male doctor, you could ask if he's ever drunk his own vomit. If he looks at all shocked at the suggestion, he hasn't been to a UK medical school.