Security chiefs on both sides of the Atlantic repeatedly turned down the chance to acquire a vast intelligence database on Osama bin Laden and more than 200 leading members of his al-Qaeda terrorist network in the years leading up to the 11 September attacks. They were offered thick files, with photographs and detailed biographies of many of his principal cadres, and vital information about al-Qaeda's financial interests in many parts of the globe. On two separate occasions, they were given an opportunity to extradite or interview key bin Laden operatives who had been arrested in Africa because they appeared to be planning terrorist atrocities. None of the offers, made regularly from the start of 1995, was taken up. One senior CIA source admitted last night: 'This represents the worst single intelligence failure in this whole terrible business.' Bin Laden and his cadres came to Sudan in 1992 because at that time it was one of the few Islamic countries where they did not need visas. He used his time there to build a lucrative web of legitimate businesses, and to seed a far-flung financial network - much of which was monitored by the Sudanese. They also kept his followers under close surveillance. One US source who has seen the files on bin Laden's men in Khartoum said some were 'an inch and a half thick'. They included photographs, and information on their families, backgrounds and contacts.