Thousands of Londoners are likely to face severe train delays until the end of the week following "extensive" damage to overhead power cables.
The problems at Radlett in Hertfordshire have affected the services of three train companies in the capital.
Paul Brand has been speaking to Mick Cash from the RMT union and to passengers affected by the delays.
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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.