Johnston had seen diplomatic service in Germany, first as King's envoy to Berlin and later working to secure the Hanoverian succession, and made frequent journeys to Hanover.

It was also said "he keeps out a very great rank, and frequently has Mr. Walpool and the greatest courtiers with him at his country house near London; and the King sometimes does him the honour to dine with him".

He procured a lease (from the then under-lessee Mrs Davies)[note 1] and commissioned architect John James to plan and erect a mansion – a project which spanned the following 35 years.

[7] A baroque octagonal room, designed by architect James Gibbs, was added in 1720 for entertaining George II's Queen Consort, Caroline, who regarded Johnston with great favour.

[14] Orleans House Gallery, which opened in 1972,[15][16] displays material from the London Borough of Richmond upon Thames' art collection.

[18] The gallery's previous exhibitions have included watercolours and sketches by Richard Dadd[19] and, in 2003, the first major retrospective of Stephen Wiltshire's works.