The house at 44 Berkeley Square was built in 1740 (to the design of the architect William Kent) by Lady Isabella Finch (1700-1771), the 7th daughter of Daniel Finch, 7th Earl of Winchilsea, 2nd Earl of Nottingham (1647–1730). It is famed for its theatrical staircase and large Grand Saloon, "one of the finest rooms of its scale and period in London", the design of which was based on the famous Double Cube Room at Wilton House in Wiltshire.] She never married but became Lady of the Bedchamber to Princess Amelia, a spinster aunt of King George III. It was purchased after her death by William Henry Fortescue, 1st Earl of Clermont (1722-1806), an Irish peer, and served as his London townhouse and eventually housed the Clermont Club - founded by John Aspinall. - https://en.wikipedia.org/wiki/Clermont_Club
Aspinall's friend, Mark Birley, founded the nightclub Annabel's in the basement after "Aspinall decided they needed somewhere to party after an evening's gambling". In 2016 Annabel's was moved to 46 Berkely Square. 44 Berkely Square now serves as an event space . Annabel's is one of two nightclubs visited by the queen. The interior was originally designed by Mark Birley and was since updated by his daughter, India Jane.