MI5 is much enhanced since Crevice: but it still can’t make guarantees

For almost two years, Westminster has been abuzz with what many MPs believed to be an explosive secret. The ringleader of the 7 July London bombings, Mohammed Sidique Khan, was not a so-called ‘clean skin’ who came out of the blue. Instead, he had been bugged, photographed and followed during an MI5 investigation into a thwarted fertiliser-bomb plot more than a year earlier.