The trial of two men charged with the murder of oil executive Carole Waugh, whose body was found with a single stab wound inside a car at a garage in south-west London in August 2012, is due to begin today.
Rakesh Bhayani, 40, and Nicholas Kutner, 47, are charged with murdering the 50-year-old, who disappeared from her central London home.
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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.