Sources said that the Docklands property giant was in “serious” discussions with BT over buying the site, which attracted strong initial interest before Christmas. Negotiations are said to focus on Canary Wharf bolstering BT with a knock-out price for the building while luring the business as its biggest tenant so far at its Wood Wharf development which is under construction and comprises 2 million square feet of office space and 3300 homes.