Massive fat mounds removed from London's sewers
14 July 2010 Last updated at 16:46 BST
Thames Water says it has removed enough fat to fill nine double decker buses from London's sewers.
The company said the clean-up operation, beneath Leicester Square, was the largest of its kind.
The build-up of fat, caused by people pouring substances like cooking fat down the drain, causes flooding in 7,000 homes in the capital every year, Thames Water added.
The BBC's Matt Cooke took a trip below ground to see the problem.