Braving rain and an extremely muddy pitch, the Prime Minister - who said he used to play the position of hooker - passed a rugby ball around with children who were having a taster session at Millwall Rugby Club in east London.
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Nigel Farage warned on Friday Britain was "far less safe" and exposed to Cologne-style sex attacks because of open-door immigration.
Arthur Simpson-Kent, 48, admitted killing Ms Blake and their sons according to his lawyer.
Two brothers have been arrested on suspicion of murder after their parents were found dead in their own home over the weekend.