In an unprecedented campaign, police are attempting to enlist Muslim mothers to stop their sons going to war.
With hundreds of young British men fighting in Syria, security chiefs believe they could return radicalised and dangerous. They want women to persuade and even inform on their relatives.
ITV News' UK Editor Lucy Manning reports:
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The suspect, 35-year-old Willie Corey Godbolt, has been arrested and was being treated for a gunshot wound in hospital.
Mohanna Abdhou, known as Montana, was out with friends when two attackers cycled up to them and opened fire in Brent, north-west London.
The US president tweeted that Mrs May gave him "full details" of the incident during talks while he attended summits in Europe.