Mount Street

Mount Street, London

Mount Street is in Mayfair, near Hyde Park, and as this map shows is still there in the 1990's, as this is a current map taken from the website http://uk.multimap.com/map

John Carlyon was in Mount Street when he was working in London, but I don't recall the book saying that this was the Carlyon's town house, or whether John, like Eustace Cheviot, just rented rooms there.