It's emerged the flood in Herne Hill will cost Thames Water and its insurers around four million pounds.
Dozens of businesses and homes were left under water on Half Moon Lane early on Wednesday morning after a pipe burst.
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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.
Catherine Burke's body was discovered at a house in a quiet street in Muswell Hill last Thursday evening.