[2] The original building was constructed in the mid 18th-century; what today comprises Dartmouth House was two separate residences, numbers 37 and 38 Charles Street.

Many of Lord Revelstoke's furnishings and objects d’art had to be sold at auction, although he continued to live here until his death in 1897.

The next owner, William Legge, 6th Earl of Dartmouth, made the most significant changes to the interior of the house in 1900, with the creation of the Long[7] and Small Drawing Rooms.

[8] The house was used as the Dartmouth family home until the outbreak of war in 1914, when it was used by the British Red Cross as a military hospital.

It was formally opened as the London Headquarters of the ESU by the Prime Minister, Sir Stanley Baldwin, on the 22 February 1927.