In net-curtained rooms above a disused kebab shop on Cricklewood Broadway, a small group of middle-aged men were at work as usual when they found themselves at the centre of a national terror warning.

In offices sandwiched between a TV repair shop and a hair salon in the north-west London suburb, the men produce an Arabic-language site supporting Egypt's now banned Muslim Brotherhood.

At the same time, the prime minister announced a high-level investigation into whether the group – one of the Arab world's most powerful political organisations – was heading towards "violent extremism" in Britain and elsewhere.

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