The estate's development dates from 1715 when speculative planning of
Cavendish Square in London, and the streets around it began. The Marylebone manor and estate was purchased by the
Duke of Newcastle in 1711. Dying soon after, the estate passed to his daughter
Henrietta Cavendish Holles who married
Edward Harley, heir of the Earl of Oxford, in 1713. Both Edward's father and uncle were active and influential in English politics during Queen Anne's reign and it seems that his uncle Edward was behind the appointment of a steward and surveyor to begin marking out building plots and negotiating leases on Henrietta's Marylebone estate. In 1719 the surveyor John Prince published a plan of the estate showing named roads and building sites which is still recognisable today. Thus began a programme of building fashionable properties extending north from Tyburn Road, renamed
Oxford Street, as far as Regents Park, taking in the old village of Marylebone on the west and the newly built Cleveland Street on the east. The estate was inherited by Henrietta and Edward's only child, a daughter,
Margaret Cavendish-Harley, who in 1734 had married
William Bentinck, 2nd Duke of Portland. The building continued and it became known as the Portland Estate, passing through successive Dukes. ==Property==