Boris Johnson is expected to visit the Crossrail site at Tottenham court road later.
The mayor will be questioned on yesterday's government spending review.
A commitment of £2 million was made to look into the north-south rail link for cross rail 2 in yesterday's spending report by George Osborne.
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If you've been anywhere near Trafalgar Square today you'll notice something different.
Look closely at this collection of images by photographer Jim Grover and you'll notice there's something missing.
Sir Bernard Hogan-Howe's decision to retire comes after growing speculation about his future and his relationship with mayor Sadiq Khan.