The Bank of England was due to select the buyer for Bank Buildings on 1 Lothbury, EC2, this week.
The Bank initially intended to select the buyer for the core development site two weeks ago, but decided to carry out a second round of bids between three parties after receiving bids in excess of £26m.
Drivers Jonas, which was marketing the site, gave a guide price of £15m-£20m.
It is believed that a joint venture between serviced office operator HQ Global Workspaces and US private equity house Babcock & Brown was competing against the Howard de Walden Estate, the major landowner of the Marylebone area.
The family behind the West End estate is fourth in the EG Rich List, with an estimated wealth of £1.3bn, and has been looking to enter the City for more than a year.
Lapur Investments, the Jersey-based family trust that paid £27m for the former Midland headquarters at 27 Poultry, EC2, in January, also bid.
Meanwhile, US developer Tishman Speyer is still in negotiations with two developers over the sale of its east London estate, Aldgate Union, E1, following the collapse of talks with Allied London last week.
While Tishman’s adviser CBRE has said that the building has been officially withdrawn from the market, the developer is believed to be in detailed negotiations with an American developer and Australian developer Multiplex.
Also this week, David Khalili’s Favermead Assets had a meeting concerning Bath House on Holborn Viaduct, EC1, after an aborted sale to Meyer Bergman.
Favermead, advised by Nelson Bakewell, will decide whether to sell to an underbidder, restructure its financing on the building or apply for a new planning consent.