In March 1635 he was appointed master of the court of wards, and his exactions in this office were a principal cause of the unpopularity of the government. He was also appointed a commissioner for the treasury, together with Laud. Between Cottington and the latter there sprang up a fierce rivalry. In these personal encounters Cottington had nearly always the advantage, for he practised great reserve and possessed great powers of self-command, an extraordinary talent for dissembling and a fund of humour. Laud completely lacked these qualities, and though really possessing much greater influence with Charles, he was often embarrassed and sometimes exposed to ridicule by his opponent. The aim of Cottington's ambition was the place of lord treasurer, but Laud finally triumphed and secured it for his own nominee, Bishop Juxon, when Cottington became "no more a leader but meddled with his particular duties only."[1] He continued, however, to take a large share in public business and served on the committees for foreign, Irish and Scottish affairs. In the last, appointed in July 1638, he supported the war, and in May 1640, after the dismissal of the Short Parliament, he declared it his opinion that at such a crisis the king might levy money without the Parliament. His attempts to get funds from the city were unsuccessful, and he had recourse instead to a speculation in pepper. He had been appointed constable of the Tower, and he now prepared the fortress for a siege. In the trial of Strafford in 1641 Cottington denied on oath that he had heard him use the incriminating words about "reducing this kingdom." When the parliamentary opposition became too strong to be any longer defied, Cottington, as one of those who had chiefly incurred their hostility, hastened to retire from the administration, giving up the court of wards in May 1641 and the chancellorship of the exchequer in January 1642. He rejoined the king in 1643, took part in the proceedings of the Oxford parliament, and was made lord treasurer on the 3rd of October 1643. He signed the surrender of Oxford in July 1646, and being excepted from the indemnity retired abroad. He joined Prince Charles at the Hague in 1648, and became one of his counsellors. In 1649, together with Hyde, Cottington went on a mission to Spain to obtain help for the royal cause, having an interview with Mazarin at Paris on the way. They met, however, with an extremely ill reception, and Cottington found he had completely lost his popularity at the Spanish court, one cause being his shortcomings and waverings in the matter of religion. He now announced his intention of remaining in Spain and of keeping faithful to Roman Catholicism, and took up his residence at Valladolid, where he was maintained by the Jesuits. He died there on the 19th of June 1652, his body being subsequently buried in Westminster Abbey. He had amassed a large fortune and built two magnificent houses at Hanworth and Founthill. Cottington was evidently a man of considerable ability, but the foreign policy pursued by him was opposed to the national interests and futile in itself. According to Clarendon's verdict "he left behind him a greater esteem of his parts than love of his person." He married in 1623 Anne, daughter of Sir William Meredith and widow of Sir Robert Brett. All his children predeceased him, and his title became extinct at his death.