Mohammed Hamid, 50, of east London, was found guilty of training men in secret camps in the Lake District and New Forest to prepare them to fight abroad.

Among those to have passed through Hamid's camps were the four failed suicide bombers of 21 July 2005.

All four of the men responsible for the failed bombings were friends of Hamid.

The conviction marks a major success for counter-terrorism policing with Hamid regarded as a key figure in extremist networks.

Police say Hamid played a crucial role in grooming young men for terrorism and possible training overseas.

It will be their final encounter before next week's crucial primaries in Ohio and Texas.

Mr Obama is regarded as the front-runner, after winning the previous 11 primaries and caucuses.

Ahead of the debate he won endorsement from a former rival for the Democratic nomination, Senator Christopher Dodd.

Mr Dodd, who abandoned his bid last month, is the first Democratic campaign drop-out to endorse another candidate.

On Tuesday he and Mr Obama appeared at a joint news conference in Cleveland, Ohio, where the debate will be held at 0200 GMT.

Christopher Dodd is fully behind Barack Obama

Mr Dod

The footage showed a man making an appeal to Prime Minister Gordon Brown to help secure the hostages' freedom.

"My name is Peter Moore, I have been held here for nearly eight months now," the man said in English.

He asks Mr Brown to free nine Iraqis in exchange for the release of the Britons seized in May 2007. The Foreign Office has condemned the release of the video.

The video shows the man speaking in English with an Arabic translation played over the top.

'Simple exchange'

The man appealed for the freedom of the Iraqis prisoners - being held by the coalition authorities.

"All I want is to leave this place. I tell Gordon Brown the matter is simple: