Dave Dennis, Thames Water sewer operations manager, said the blockage was comprised of cooking fats that had been poured down the city's drains and hardened along with debris including wet wipes, tennis balls and pieces of wood.
"We have 67,108 miles of sewers, and that's a lot of pipe to keep clear," Dennis said. "We spend 12 million pounds a year tackling blockages, most of them formed because people have tipped cooking fats down the drain and wet wipes down the loo. The sewers serve an important purpose -- they are not an abyss for household rubbish."
Dennis said workers used high-powered jets to break up the fat and clear the blockage beneath a street in Shepherd's Bush, West London.
"Fat goes down the drain easily enough, but when it hits the cold sewers, it hardens into disgusting fatbergs that block pipes," he said.
"We have found all sorts in this sewer -- from tennis balls to planks of wood," Dennis said. "It goes without saying they shouldn't be in those pipes. London -- bin it, don't block it."