Real estate group British Land has completed its third letting in three months at Marble Arch House in Central London.NERA Economic Consulting has agreed to rent out the 11,500 square foot third floor of the building, located on Seymour Street in the West End.The company has signed a 10-year lease at a price of £72.50 per square foot."Having launched the space in the spring, the leasing programme has gathered real momentum with three significant deals completed in as many months," said James Danby, head of office leasing at British Land.He said that the latest deal puts the building close to being 50% let."We continue to see high levels of interest reflecting the building's excellent design and location."British Land bought and redeveloped the 61,236 square foot Marble Arch House building in 2011, comprising mainly office.BC