Portland Place is named after William Bentink, 2nd Duke of Portland, who inherited the land on his marriage to Lady Margaret Cavendish Harley in 1734.
Work began in 1773 with two of the leading architects of the time, Robert and James Adam. The houses were originally intended to be a series of private palaces, though it was quickly realised that this was too ambitious and uneconomical, and the large, detached houses were redesigned as more modest terraces.
Originally, the street was closed at the northern end by Marylebone Fields and at the southern end by Foley House, and access was by side street only. It is still one of the widest streets in London, and it is said that this was to ensure that the new houses didn’t block the view of Hampstead and Highgate from Foley House.
Work on the terrace incorporating No.21 began in 1776 and was completed in 1778. The house would have been used as a social residence and alternative to country estates during the social seasons and Parliamentary terms.