From the Wikipedia page [1]
The Holly Lodge Estate is an estate located on the site and grounds of a villa built in 1798 by Sir Henry Tempest on the south-facing slopes of Highgate, London adjacent to Highgate Rise, now known as Highgate West Hill. The estate lands included Traitor's Hill, reputedly where members of the gunpowder plot had met to watch the Palace of Westminster blow up although since known to be false. This villa was later to be known as The Holly Lodge and in 1809 a young actress, Harriot Mellon, took over the lease on the property. She married the banker Thomas Coutts in 1815 and enlarged the house and grounds by buying adjacent properties. The grounds were landscaped by John Buonarotti Papworth in 1825. When Harriot Mellon died in 1837 she left the house and her fortune to Mr Coutts' granddaughter, Angela Burdett.
The website is [2].