Thames Water said a huge fatberg weighing 63 tonnes – several tonnes of which was concrete – was cleared from a Pall Mall sewer after being broken up by engineers with power tools and then their hands.

Another weighing 30 tonnes and stretching 70 metres was removed from the sewers of Cathedral Street, near the Shard.

The two fatbergs were threatening to flood homes and businesses with wastewater over the festive period, the water supplier said.

Fatbergs are formed when fat, oil and grease are poured down sinks and drains, and combine with items that should not be flushed down the toilet, such as unflushable wet wipes, nappies and cotton buds.

Thames Water asked people not to “feed the fatberg” over Christmas, saying the two discoveries served as a timely reminder about the importance of properly disposing of cooking fat.

The two fatbergs come just months after Thames Water had to remove a 100-metre “Concreteberg” from underneath Islington, while a 40-tonne fatberg the size of a double-decker bus was cleared from a Greenwich sewer in November.

-AAP