The £1bn purchase of Britain’s second tallest tower, 25 Canada Square, in London’s Canary Wharf remains uncompleted after four months it was agreed.

The Royal Bank of Scotland (RBS) agreed in July to sell the headquarters of Citigroup to a consortium of investors including financier Derek Quinlan and private property group Propinvest.

RBS bought the building and its neighbour, 5 Canada Square which sold in July for £453m, for £1bn in December 2003. But should the transaction fail, it would be one of a string of property deals to flounder in recent weeks, which could be a sign of how the credit squeeze has affected the real estate market.

Last month saw an Aim-listed property company, Delek Global Real Estate, withdraw from the £1.4bn purchase of a portfolio of 88 buildings owned by Jelmoli, a Swiss retailer