Robert produced an important plan that proposed filling an old center court with a vast domed pantheon-like hall; it was never executed, however. The entrance hall of Syon, based on a basilica—a rectangular building divided into three areas by two rows of columns—with its half-domed ends, is one of the most significant Neo-classical interiors in England.
Other houses ; from this early phase include the first completely new house, Mersham-le-Hatch, Kent (1762-72); Lansdowne House, Berkeley Square, London (1762-68); Luton Hoo, Bedfordshire (1766-75); Newby Hall Yorkshire (c.1767-85); and Kendwood, London (1767-68).
The south front of Kedlesion Hall provides an example of Adam’s exterior treatment. His theme of a triumphal arch as the exterior expressions of the great domed interior hall is the first use of this particular Roman form in domestic architecture. The double portico (an open space created by a roof held up by columns) at Osterley Park, derived from the Portico of Octavia, Rome, is a similar Neoclassical motif.
In 1768 Robert and James Adam leased a site on the Thames for a speculative development to be known as the Adelphi (it was almost totally destroyed in 1836). They invested a large sum on embanking the side and building several terraces of houses (1768-72) in which the Adam interior style of slip- pilasters supporting a shallow frieze and cornice—the middle and uppermost sections of an entablature—was brought out of doors. It was, however, a financial disaster. In 1773 they again speculated unsuccessfully in a group of stuccoed terraces in Portland Place, London.
The Adams build three major London houses in the early 1770s, which were superb examples of their mature style—No. 20, St. James’s Square for Sir Watkin Williams-Wynn (1772-74); No. 20, Portman Square for the Countess of Home (1775-77; now the Courtauld Institute of Art); and Derby house in Grosvenor Square for the Earl of Derby (1773-74; demolished 1862).
In 1773 they published the first volume of the Works in Architecture of Robert and James Adam. A second volume followed in 1779, a third was published post-humously in 1822. In the preface to the firs volume they explain their idea of “movement,” an essential aspect of the Adam style:
Movement is meant to express, the rise and fall, the advance and recess, with other diversity of form, in the different parts of a building, so as to add greatly to the picturesque of the composition. (S.Mi.)