The Queen arrived at Kensington Palace today to visit the Duke and Duchess of Cambridge and their new son.
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The pair filmed themselves clinging on as the train travelled from Essex to London at high speed.
Around 60 firefighters tackled the blaze at the four-storey building in Daleham Gardens, Hampstead, that broke out early on Tuesday.
It is the fourth time in five years that the London borough has topped the rankings, according to data from the ONS.