Developer British Land revealed the latest failure as it confirmed a programme to replace “a number of bolts” on the Cheesegrater tower.

Two bolts broke last November leading to an area around the base of the building being cordoned off and safety netting installed to protect pedestrians.

British Land said: “A third bolt fractured recently and was captured by precautionary tethering put in place last year.”

Investigations into the problem have been carried-out by main contractor Laing O’Rourke and structural engineer Arup.

British Land said: “A programme to replace a number of bolts will take place as a precautionary measure.”

It added the probe revealed “that the problem is limited to certain bolts. Arup has also confirmed that there is no adverse effect on the structural integrity of the building.”

The developer declined to confirm the exact number of bolts being replaced but precautionary measures are believed to be being taken on “mega-bolts” on eleven floors of the 47-storey building.

Laboratory testing of the broken bolts – which are the size of an arm – “concluded that the bolts had fractured due to a material failure mechanism called Hydrogen Embrittlement. This is a crack growth mechanism within the bolt material.”

British Land added: “As the problem has been identified and is being rectified no further update is scheduled.”