Returning to Europe, he studied architecture in Paris and Italy, Then in 1755 he returned to England and established an architectural practice in London. He was appoined architectural tutor to the Prince of Wales, later George III, and also, with Robert Adam, Architect of the Kings Works. In 1757 he published a book, of Chinese designs which had quite an influence on contemporary taste.
He was influenced by continental styles when designing for English clients. His most famous building is Somerset House in London.
He was born in Peebles and came to Edinburgh in 1814 to work in the bookselling trade. He opened his own shop in 1819 and branched out into printing. With his younger brother, Robert, he produced books of Scottish interest, such as Gazetteer of Scotland. Their publishing business prospered, and in 1859 - the year in which Chambers Encyclopaedia saw the light - he founded a museum and art gallery in Peebles. As Lord Provost of Edinburgh from 1865 to 1869, he was responsible for the restoration of St Giles' Cathedral.