It is understood that the group beat off strong competition from rival pub groups and restaurant chains to acquire the c7,000sq ft site, the parent company of which was placed into administration last year.
The company plans to re-open the site under a new name, The Admiralty, at the start of October.
The property currently comprises a ground floor restaurant and bar with views of the square, an intimate mezzanine restaurant, a private dining room, and a vaulted cocktail bar and live music club – the A-Lounge.
It will become a sister location for the group’s recently refurbished Red Lion in Parliament Square. The group recently launched a new menu for its 14 Ale & Pie sites.
Christie + Co acted on behalf of the administrators.