The family of a Sussex man jailed for life for smuggling heroin out of Thailand today vowed to fight for his release.

English language teacher Julian Gilbey, 35, who emigrated to South East Asia from West Grinstead, near Horsham, narrowly escaped a death sentence because he admitted smuggling.

He was found with 4kg of heroin but claimed he thought he was carrying diamonds.

Mr Gilbey was one of four people who appeared in court in Bangkok.

He was born in Scotland and taught English at schools in Sussex before moving to Thailand two years ago.

His relatives insist he was duped into carrying the drugs.

Karen Cameron said her brother's claim about the diamonds was never heard in court and the hearing had not been fair.

Speaking at her home in Rothesay, Isle of Bute, she said officials from the British Embassy had contacted the family this morning.

She said evidence from a key witness was thrown out of court which would have shown Mr Gilbey was unaware he was transporting drugs.

The witness, John Care, was acquitted of the same charge by a court in Austria, which accepted he had been duped by the gang into thinking he was smuggling diamonds.

However, the Thai court insisted Mr Care should give evidence in person.

He has been advised not to travel to the country for his own safety, Mrs Cameron said.

She said: "Although there was evidence to say Julian thought he'd been carrying diamonds, that wasn't allowed in court.

"His lawyer asked the judge to accept letters from the Austrian judge and from John Care himself, but he said no."

Mrs Cameron, 37, said it was a "tremendous shock" for the family when they were told 11 months ago that Mr Gilbey had been arrested for drug smuggling.

She said: "When Julian was last home two years ago he talked about the corruption in Thailand and the drugs scene.

"He said you'd have to be stupid to get involved in drugs out there. He's done something very stupid, but he doesn't deserve the sentence he got. He has not had a fair trial."

Since his arrest Mr Gilbey has been remanded in the infamous Bangkok Hilton jail, but today he was transferred to a maximum security prison following his conviction.

Mrs Cameron said: "Julian writes quite regularly, but he doesn't put too much in his letters about the conditions because he doesn't want to distress his family.

"He's sewn 16 blankets together to sleep on and he was in manacles for ten months. They're now back on and they're welded on.

"We send food parcels out to him and he gets money sent out but the conditions aren't very pleasant. He has been in cells with 30 to 40 people in a room."

Alan Reid, Liberal Democrat MP for Argyll and Bute, is leading calls for a review of the case.

He is particularly concerned because the conviction is based on a signed confession by Mr Gilbey, written in Thai.

Mr Reid said: "Under Thai law it should have been presented in English but Julian insists it was never translated for him."

Mr Reid said Britons convicted in Thailand could be returned to the UK after serving a third of their sentence and hoped Mr Gilbey could be moved.