It was sold to its second owner, 4th Duke of Marlborough, in 1786 it was bought by William G. Hamilton and altered to a neoclassical house by Robert Adam.

[3] In the second half of the 1870s the property was bought by John Beal, a well-known stationer of East Street, who used the basement rooms for storage.

[2][8] In the 1990s, Brighton and Hove City Council used Marlborough House as a tourist information centre before selling it to local businessman Tony Antoniades for £500,000 in 1999.

[9] By 2015, the building was badly water damaged and the original fireplaces had been removed to a warehouse in London, where they perished in a fire.

A representative of Historic England said "Our hands are tied to some extent if a private owner cannot or will not maintain the building – we are an advisory body.

[1] Brighton and Hove City Council issued an enforcement notice for the paint to be removed, only to be overruled by the Planning Inspectorate in 2018.

[10] By 2019, the Council confirmed it was dropping its legal actions against Antoniades because a new planning application had been made which would correct the illegal changes to the building.