A police officer on The Mall a day before the London Marathon
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London Marathon: Extra police on duty

21 April 2013 Last updated at 07:28 BST

Hundreds of extra police officers will be on duty at the London Marathon in a bid to reassure runners and spectators after the Boston bombings.

A 30-second silence will be held at the start line for the three people killed in the attacks on Monday.

Tim Allman reports.