HSBC is in talks to buy back its UK headquarters in Canary Wharf for up to £300m less than the price it sold the tower to Spanish property company Metrovacesa only a year ago.

Metrovacesa has until the end of November to refinance a £810m loan with HSBC on the tower, which became Britain's most expensive building when it was acquired in a £1.1bn sale-and-leaseback deal at the peak of the property boom last summer.