Olympic gold medallist Ed McKeever receives a briefing ahead of his participation in the Big Waterways Clean Up Project on the Lea Navigation in East London today.
Three and a half thousand volunteers have taken part in the scheme to tidy up waterways in the five Olympic boroughs.
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London was today a city of sirens and half mast flags in the wake of another terror attack.
MPs said they would "carry on" and go to work "as usual" in defiance of the terrorist attack outside the Palace of Westminster.
A huge police operation is under way after a terror attack in Westminster.