The full scale of the terrorist threat to Britain can be revealed today with the disclosure that about 250 British-based jihadis who went to train and fight in Syria have returned home, The Sunday Times said. Senior security officials say the high number of “returnees” — five times the figure that has been previously reported — underlines the growing danger posed by “extremist tourists” going to the war-torn region. Military Intelligence, Section 5 or MI5 and police have already thwarted one serious plot last autumn by a cell of “returnee” jihadis who were allegedly preparing a Mumbai-style gun attack on civilians, probably in a crowded public place in London.