Laing O’Rourke is main contractor on the £318m building dubbed the Cheesegrater which is due for completion in mid 2014.

Joint venture developers British Land and Oxford Properties confirmed the deal this morning which will see Amlin take levels 18-24 and level 45 with options to take up to a further 36,500 sq ft.

Fellow insurance firm Aon has already signed a deal to take 191,000 sq ft of space across the lower ten floors of the completed building.

Richard Hextall, Amlin Group Finance & Operations Director, said: “We have conducted a thorough review of our future accommodation options together with Savills over the past year and have decided that The Leadenhall Building will provide the best solution for our expanding Group and London operations.

“Leadenhall will provide our staff with perfectly located offices in this elegant, high rise building and we look forward to moving to our new headquarters in 2015.”

Tim Roberts, Head of Offices at British Land said, “We are delighted that Amlin has chosen The Leadenhall Building for its new offices. This will be our second major pre-letting at the building and it shows the considerable appeal of our offer – highly specified and well located buildings of strong architectural quality coupled with a commitment to occupier service.”

Paul Brundage, Executive Vice President, Senior Managing Director Europe of Oxford Properties said, “This major letting to Amlin is further testament to the world class credentials of The Leadenhall Building – both in terms of the location and prestige of the building itself and the flexibility and quality of the space on offer.

“This second, significant pre-letting also demonstrates the strength of our joint venture with British Land.”