Ten Trinity Square, a listed building which overlooks the Tower of London, is to be turned into a luxury hotel by US developer Thomas Enterprises.

The building, currently the global headquarters of insurance group Willis, was bought by Thomas Enterprises for an estimated £110m.

The developer is expected to spend a reported £150m to convert the property into a hotel with more than 100 bedrooms and 30 apartments alongside exclusive health and spa facilities.

Joe Plumeri, chair and CEO of Willis, said: “We are delighted to be leaving the beautiful old building in the capable hands of Thomas Enterprises, who we are sure will do this renowned landmark justice.”

Willis bought the property in 1976, and put it up for sale last year through its property agent Atisreal. It will vacate Trinity Square in 2008.

Ten Trinity Square was first was opened in 1922 as the headquarters of the Port of London Authority. Although the inner rotunda was bombed during the Second World War, the outer structure of the building remained intact, and the building hosted the inaugural reception meeting of the General Assembly of the United Nations in 1946. Details: www.willis.com