Those looking for the outward signs that identify them as full of hatred would be hard-pressed to find them. Many seem all too ordinary, perhaps enthusiastic about football and cricket and living “normal” westernised existences in neat terraced houses. Most show little indication that they have signed up to the distorted ideology of radical Islam, with its millennial ideology of bringing destruction to the corrupt West. As “sleepers”, they are perfect.

That Britain has become a breeding ground for these young men can be ascribed to timidity on behalf of the authorities, wedded as they are to a multiculturalism that isolates many young men in ghettos. The United States, with its intolerant attitude to those preaching hate, has been far more successful in integrating its Muslim citizens, offering them the ideals of patriotism and progress. Even France, which has a bigger Muslim population than Britain has not seen the scale of Islamist treachery now being experienced.

The great challenge for Britain is to minimise the future risks. Nobody should underestimate the scale of the problem or the time needed. The country already has a generation of disaffected Muslims who see any excuse as a reason for killing their fellow citizens. This low-level war is going to take a huge effort of will and courage. It is going to mean applying what may seem illiberal measures in order to save lives. In return, the state must exercise massive restraint and ensure it does not abuse that responsibility.

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