The police presence around Oxford Street has been stepped up after a 'smash and grab' raid on Selfridges last night. Detectives say they are reviewing CCTV footage from the time of the burglary.
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The plaque at number 16 Cowley Street in Westminster marks the brown brick Georgian townhouse where Sir John lived for 31 years.
A man reportedly armed with several knives has been arrested in Whitehall on suspicion of planning a terror attack, police have said.
Metropolitan Police officer, Tom Harrison, has been crawling the course since the race began on Sunday morning.