We’ve all heard of dodgy handbags or knock-off designer T-shirts and that Viagra picked up in a nightclub might not be kosher, but few of us would ever dream that the prescription medicines we get from our chemist might be counterfeit. However, the truth is that fake medicines are a growing global problem. The World Health Organisation (WHO) estimates that 10 per cent of all the drugs traded worldwide are now counterfeit with lethal consequences, and Britain is not immune.

You might have assumed that there was some sort of central NHS clearing house for the purchase of medicines. Not so. Hospital trusts and retail pharmacists are free to buy medicines through any legal route to find the best price. Purchasing cheaper drugs through “parallel traders” — companies that source them from other countries where the drugs are substantially cheaper than ours — is good news for them, and 90 per cent of pharmacists do so. But the consignments may pass through dozens of hands before reaching legitimate parallel traders, acquiring anonymity in the process.

Thus parallel traders can be entirely innocent of the provenance of the medicine they sell, and this is when drugs can be switched with fakes or even placebos, the consequences of which can be distressing or sometimes even fatal.

For instance, GlaxoSmithKline (GSK) made a large quantity of low-cost anti-retroviral Aids drugs available to several African countries. The drugs, desperately needed by Africans, and with a value of £18 million, promptly found their way back to Europe, where they were sold at a much higher conventional price in new packaging to European customers, including the NHS, by an innocent parallel trader.

Someone made a killing. Literally. But when the case came to the Court of Appeal, in March 2004, GSK failed to make any progress in preventing it happening again.

These were the real thing in genuine-looking packaging. Another form of counterfeiting is those medicines that are chemically identical to branded medicines, usually sourced from India or China, which have been repackaged to look like the genuine article. They are functional but fake, the medicinal equivalent of the Gucci handbag for a fiver in the market.

But there are also medicines that are bogus, containing little or none of the medication, yet in convincing, high-quality reproductions of the genuine packets, right down to the security holograms. This is the medicinal equivalent of a loaded gun. The criminals who make them are not concerned with consequences, just the huge profits — $32 billion (£18 billion) worldwide is the estimated profit for these high-demand, low-cost items.

Surely we could spot fakes quickly? It’s not as easy as you think. Consider statins, the cholesterol-lowering drugs. If someone who has been taking fake tablets for a year returns to their doctor with a stubbornly high cholesterol level, what would they think? That the patient hadn’t been taking them as directed (very common)? Hadn’t been eating the right food? Perhaps that he was one of the small percentage for whom these drugs don’t work well? The last thing the doctor would suspect is that the tablets were fake. It’s a perfect crime. And before you think this far-fetched, in 2003 American police found 200,000 packets of fake Lipitor — a bestselling statin — which led to the recall of thousands of bottles of the drug.

Even life-saving medicines are at risk of being counterfeited. Streptokinase is used to treat heart attacks. A German investigation of 21 formulations of Streptokinase bought across the world, and published in the European Heart Journal two months ago, revealed that only three were full strength; one brand had just 20 per cent of required activity.

And, in a harrowing film for BBC Two, This World: Bad Medicine, to be shown on Tuesday, an American paediatric heart team working in Nigeria discovered that they were using fake adrenalin when children began to die.

But we’d spot something like that in Britain, wouldn’t we? Not necessarily: these sort of drugs are being given by doctors and pharmacists to critically ill patients, in whom death is frequent. Sub-standard counterfeit drugs wouldn’t immediately spring to mind as a cause of death. And since medicines may pass through 30 or more separate middlemen before being dispensed, bad gets mixed in with good and the chances of discovery are reduced further.

I asked an expert in counterfeit medicines, Graham Satchwell, an ex-policeman and the principal investigator in the GSK Aids drugs case, how much fake medicine was circulating in Britain. “We just don’t know,” he said. “That’s because there is no method in the UK (or much of Europe either) that can identify fake pharmaceuticals before they are dispensed.” And even if there are adverse reactions to sub-standard drugs, there is nowhere to report them to.

He points out that all the findings of counterfeit medicines in Britain to date have been accidental. “If you don’t look, you won’t find anything.”

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