David Chell, the nurse sentenced to death in Malaysia for drug smuggling, is one of thousands of Britons convicted abroad. Some are guilty, others just naïve. It is the stuff of travellers' nightmares - getting thrown into a squalid prison, facing a stiff penalty for unwittingly acting as a drugs courier.

About 2,600 Britons are in prison abroad, the majority on drugs charges.

Most are held in Europe or the United States and in 95% of cases, the defendants get a fair hearing. But others are not so fortunate, says Stephen Jakobi, of the human rights group Fair Trials Abroad.

Some are convicted on questionable police evidence. Others have no lawyer to argue their case in court, or are presumed guilty because they have had unwittingly links with known criminals during their travels.

"That's the main problem - guilt by association," says Mr Jakobi.

At present, he is working on about 40 cases involving drugs charges, including lorry drivers Allen Davis, 59, from Dorset - now serving his 11th year in a Thai jail - and Steve Bryant, 48, from Essex, who was locked up in Morocco for seven years.

Police raid

Mr Jakobi finds the case of Rachel McGee, a 24-year-old Londoner facing 15 years in a Cuban jail, particularly disturbing.

In October 1998, Ms McGee accepted the offer of cheap flight to Cuba from Karite Clacher, a friend of a man she had been dating. Police arrested Clacher and two acquaintances in a raid on their hotel, tipped off by drug smugglers who arrived from Jamaica with 15kg of cocaine. Ms McGee, who was just leaving in a taxi to sort out her visa, turned back when she saw police forcing Clacher against a wall, and was also arrested.

The authorities found no drugs on her. Yet she was convicted in a trial conducted wholly in Spanish, in which the prosecution never mentioned her name.

"The best way to ensure that innocent people don't go to jail is to have a lawyer to challenge the police case. Rachel McGee had no lawyer at all," says Mr Jakobi.

"It is guilt by association. What is truly frightening about this case is that it really could have happened to anyone going on holiday."

Of the 30 young British women held in Fort Augustus prison in Kingston, Jamaica, most face drug smuggling charges and most tell a similar tale.

Among them is Lisa Burnett, serving a 15-month sentence for smuggling cocaine, but due for early release in September.

The 21-year-old says she was duped into acting as a drugs courier after accepting a free holiday from a friend.

In 1990, Birmingham teenagers Karen Smith and Patricia Cahill went to Thailand on holiday after a British man they hardly knew offered to pick up the tab.

Both girls served three years in prison after being caught with 66kg of heroin hidden in their luggage, the biggest haul recorded. Mr Jakobi offered his services after hearing of their plight on a radio news bulletin - his first foray into securing fair trials abroad.

"My first thought was, it must be a joke. Drug smugglers don't trust teenage girls with bags of heroin. It doesn't happen like that."

Bangkok Hilton

Some of the British tourists held overseas return with horror stories about the conditions in which they were held.

In March, a British couple on £10,000 police bail fled Thailand after they had spent three weeks in a Thai prison, on drugs charges.

Although James Gilligan, 25, confessed to possessing cannabis and opium, his roommate Judith Payne, 21, also faced six years in prison.

Neither could face the prospect of returning to the notorious Klong Prem Prison - nicknamed the Bangkok Hilton, Ms Payne said.

She had been held in a room with 80 other women.

"It was filthy. There were no toilet facilities, no room to walk around, no room to do anything. All you could do was lie down, head to foot, with the other prisoners."