Transport commentator Christian Wolmar on the day's HS2 announcements:
At this stage #hs2 estimate of £33bn can only be a guess as it was made before detailed work on routes. Off to BBC News Channel at 8 30
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The problems appear to have been caused by a power supply problem in Queen's Park in north west London, which has affected signalling.
Cloudy conditions continuing overnight, with some patchy outbreaks of rain.
The mayor has revised his proposals for a six-mile East-West cycling superhighway in a bid to cut traffic delays.