Scots-born Colonel Ian Henderson, dubbed the 'Butcher of Bahrain', spent 30 years as head of the Bahraini secret police. During this time his men allegedly detained and tortured thousands of anti-government activists.

Their activities are said to have included the ransacking of villages, sadistic sexual abuse and using power drills to maim prisoners. On many occasions they are said to have detained children without informing their parents, only to return them months later in body bags. Between 1994 and 1998 at least seven people died as a result of torture at the hands of the Bahraini regime.

Human rights organisations have collected evidence from thousands of victims of the regime who have provided horrific accounts of the torture they suffered. Yaser al-Sayegh's case is typical. 'My wrists were shackled to my ankles and they suspended me upside down from a pole,' he said. 'They then beat me on my legs and feet and face with iron bars and rubber hoses.'

Hashem Redha, a Bahrainian pro-democracy activist who now lives in Britain, said he was attacked personally by Henderson. 'He tortured me one time. He kicked me and shook me two times. He said, "If you like to be hit, we can hit you more than that".'

A Carlton documentary, Blind Eye to the Butcher, to be screened on Wednesday, reveals that despite solid evidence torture took place on many occasions, a two-year investigation by Scotland Yard's Serious Crimes Branch and questions being asked in Parliament, Henderson has never been interviewed about the allegations.

However, under international law, he would be responsible for acts of torture carried out under his command, regardless of whether he was personally involved.

A file was submitted to the Crown Prosecution Service last August but police say they are still waiting for a response.

Human Rights Watch and Amnesty International have repeatedly called for an investigation into the allegations but believe successive governments have been reluctant because of Britain's close ties with the Arab state. Britain has 85 defence staff based in Bahrain and members of the country's armed forces are invited to defence colleges in this country for training.

Since retirement, Henderson has spent much of his time living at an extensive property called Stoke Shallows on the edge of Dartmoor where his neighbours know nothing of his past. He continues to travel frequently to Bahrain where he remains an adviser.

In the programme Henderson denies allegations of torture and refused to take part in any discussion. However, he issued a statement saying there was no truth in any of the allegations.

The Home Office refused to comment on allegations of torture in Bahrain.