The 225-metre London skyscraper dubbed the Cheesegrater has lost its third steel bolt in three months, causing developer British Land to replace a number of other bolts on precautionary measures.

Designed by Rogers Stirk Harbour + Partners, the architects behind Sydney’s 8 Chifley Square, the building is officially named 122 Leadenhall and is London’s fourth-tallest building.

The building’s distinct sloping profile was designed by Richard Rogers to preserve the views of the nearby St Paul’s Cathedral and has since earned the building its ‘Cheesegrater’ nickname.

The first bolt to shatter also came loose and fell into an empty hoarding area at the side of the 47-storey tower back in November and was reported to be the size of an adult arm. The second fracture came soon after but the damage was only to a small section of the bolt which then broke off and fell inside the building.

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Contractor Laing O'Rourke and structural engineers Arup were put in charge of an investigation into why the bolts were failing and came to the conclusion that it was due to a material failure mechanism.

"The tests 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," said British Land in a statement.

The third fractured bolt was discovered during the Laing O'Rourke and Arup testing which concluded that the problem was exclusive to a certain type of bolt. These are the bolts that have since been replaced on precaution.

Designed by Graham Stirk of Rogers Stirk Harbour + Partners, 122 Leadenhall provides the highest office space in the City of London. Sixteen inclined columns and braces create an open space at the building’s entrance which reaches 28 metres in height.

Images: Richard Bryant