Two groups of marines set off from Downing Street this morning, on an epic fund raising speed march around the capital.
One team headed east to the Olympic Park, and the other set off west, past Buckingham Palace.
They were seen off by Prime Minister David Cameron and the Military Wives choir.
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In a wide-ranging Peston on Sunday interview, he said Parliament security needs reviewing and the PM's counter-terror strategy is flawed.
The terror attack carried out by Khalid Masood at Westminster that left four people dead lasted less than two minutes say police.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.