CCTV investigations in London Road, Kingston found a mound of fat the size of a bus had reduced the 70 x 48cm sewer to just 5% of its normal capacity.
Thames Water has begun repairs to 20 metres of the damaged pipe and work is expected to take up to six weeks to complete.
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Officials at Transport for London have said sorry after a bus driver left a disabled passenger stranded on the roadside.
Detectives are hunting two thugs armed with wooden stakes who left a man with multiple head fractures in a vicious attack.
Police have launched a manhunt following three attacks on women in south London that detectives say may be linked.