Lindsay, who was born in Waterford, Jamaica, was 19 and the father of a one-year-old son. His wife, Samantha Lewthwaite, 21, with whom he lived in Aylesbury, Buckinghamshire, is eight months pregnant with their second child.

FBI sources said last night that Lindsay had emerged on their “intelligence radar” recently. His name is believed to have been raised in connection with a big anti-terrorist operation in Britain last year but he was not questioned.

The sources denied previous reports that Lindsay had been monitored when he visited relatives in the United States four years ago. “This guy never got on our radar screen until very recently,” an official said.

Before his death Lindsay had been living what appeared to be a normal life with his wife and their baby son, Abdullah Shaheed Ibn-Jamal.

In the weeks before embarking on his mission, Lindsay had become a frequent visitor to the Body Flex gym. To regulars there he appeared to be an innocent newcomer, keen to improve his physique.

Where and when he turned from a peaceful father and husband into a suicide bomber has baffled the small Muslim community. One source said yesterday that Lindsay had once been a follower of Abdullah el-Faisal, a Jamaican Islamist preacher in prison in Britain for inciting his followers to kill non-Muslims.

Lindsay is understood to have come to Britain from Jamaica as a young boy and lived in Huddersfield with his mother, Mary, and his sister in a 1950s terraced house. He is said to have converted to Islam in his mid-teens. He worked as a carpet-fitter before moving south.

Ms Lewthwaite, who was born in Northern Ireland when her father was serving in the British Army, was drawn to Lindsay partly because of her longstanding interest in Islam. A former school friend said that Ms Lewthwaite had been fascinated by Islam since the age of ten when she lived among Asian neighbours on a housing estate.

She converted to Islam when she was 17, taking the name Sherafiyah, before she met Lindsay, who used the Islamic name Jamal. The couple held a wedding ceremony but Samantha’s mother, Christine, is said to have refused to attend.

Police are searching the couple’s home and other addresses in Aylesbury.

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