The £340m Leadenhall building is officially the tallest tower in the City of London after topping out this week

The £340m Cheesegrater tower has become the tallest building in the City of London after it topped out yesterday.

A ceremony to mark the topping-out of the 224-metre tall Leadenhall Building was attended by Mayor of London Boris Johnson.

Laing O’Rourke is the main contractor on the job while steel specialist Severfield Rowen built the complex structure, which has been designed on an angle in order to preserve views of St Paul’s.

Severfield Rowen has faced difficulties due to the complexity of the job and has made a £10m write-off on the project.

Designed by Rogers Stirk Harbour + Partners, the tower is being jointly developed by British Land and Oxford Properties,

The building, opposite Lloyd’s of London in the heart of the City of London, has been under construction since early 2011 and is due to complete in summer 2014.

The tower will comprise 610,000 sq ft of office space over 47 floors.