He had to decide: “Shall I lose Hope and my introduction to the great, or shall I lose Clerisseau and my taste for the grand?”
He quarreled with Hope, and the two separated. Taking rooms for himself and Clerisseau , Robert settled down to serious study, visiting, sketching, and measuring the monuments of antiquity. Among the important figures he met in Rome were the art collector Cardinal Albani and the engraver Giambattista Piranesi, who dedicated an engraving and a book to him.
In May 1755 Adam and Clerisseau left Rome and travelled to Dalmatia via Venice to visit the ruins of Diocletian’s palace at Spalatro (Split). Adam felt he
Could not help considering my knowledge of Architecture as imperfect, unless I should be able to add the observation of a private edifice of the Ancients to my study of their public works.
They spent five weeks at Spalatro, preparing the drawings that were eventually to be published in 1764 as the Ruins of the Palace of the Emperor Diocletian at Spalatro in Dalmatia.
Having nearly exhausted his money and anxious to return to England, Robert had to forgo the pleasures of further expeditions to Greece and Egypt. He returned to London in January 1758, his head full of details of Roman antiquities. The current Palladian style was losing its appeal, and the public was ready for a new architectural style. Adam lost no time in making his reputation, and by the mid 1760s he had, with the help of his younger brother James, who joined him in London in 1763, created and fully developed the Adam style. That style, which he and James later claimed had “brought about, in this country . . . a kind of revolution in the whole system of this useful and elegant art,” was marked by a then new lightness and freedom in the use of the classical elements of architecture. (S.Mi.)