A secret list of young Britons who have left to join the Iraqi terrorists’ cause has been drawn up by MI5, the Daily Mail reported on Sunday. The report said that the security service was now preparing for a ‘backwash’ of highly trained guerrilla fighters returning to Britain. It fears the group will form a new hardcore of terrorist recruiters similar to jailed cleric Abu Hamza, who came back from fighting in Afghanistan to preach hatred at the Finsbury Park mosque. Whitehall sources told the Daily Mail that the MI5 had a ‘working figure’ of 50 known British recruits involved in Iraqi terror attacks against coalition forces, but the true figure is likely to be double that number because of the difficulty in tracking movements in and out of Iraq. “Immigration officials in Britain and across Europe are being warned to be on the lookout for returning fighters,’ the source said. “These people have knowledge of weapons and are prepared to use them. They are also potential recruiters for a new generation of terrorists.” Four British Muslims blew themselves up on London’s underground trains and a bus on July 7, killing 52 people and wounding 700.Shehzad Tanweer, one of four bombers who attacked London’s subway and bus network, claimed in a video recorded before his death that the invasion had been a motivating factor. He said attacks on Britain would continue until forces were withdrawn from Afghanistan and Iraq. Britain has around 7,000 soldiers in Iraq, mainly based around the southern city of Basra.