The death of Pitt (1806) surrendered the cabinet to the Whigs, and Lord Castlereagh retired with his colleagues. The death of Fox soon shook the new administration, and their own imprudence broke it up, (1807.) The Grey and Grenville party were superseded by Perceval; and Lord Castlereagh returned to the secretaryship at war, which he held until 1809, when his duel with Canning caused the retirement of both. In the Memoir, the circumstances of this painful transaction are scarcely more than referred to; but the reply to a letter from Lord Castlereagh to the King, distinctly shows the sense of his conduct entertained in the highest quarter. "The King has no hesitation in assuring Lord Castlereagh that he has, at all times, been satisfied with the zeal and assiduity with which he has discharged the duties of the various situations which he has filled, and with the exertions which, under every difficulty, he has made for the support of his Majesty's and the country's interest. "His Majesty must ever approve of the principle which shall secure the support and protection of government to officers exposing their reputation, as well as their lives, in his service; when their characters and conduct are attacked, and aspersed on loose and insufficient grounds, without adverting to embarrassments and local difficulties, of which those on the spot alone can form an adequate judgment." This, of course, settled the royal opinion; and the ministerial confidence shortly after reposed in Lord Castlereagh, in the most conspicuous manner, fully clears his reputation from every stain. But the letter confirms one fact, hitherto not much known, yet which would alone entitle him to the lasting gratitude of the empire. In allusion to the campaign of Portugal under Moore, and the appointment of a successor, it adds,--"It was also this impression which prompted the King to acquiesce in the appointment of so young a lieutenant-general as Lord Wellington to the command of the troops in Portugal." Thus, it is to Lord Castlereagh's sense of talent, and to his public zeal, that we ministerially owe the liberation of the Peninsula. His selection of the great duke, in defiance of the claims of seniority, and probably of parliamentary connexion, gave England seven years of victory, and finally gave Europe the crowning triumph of Waterloo. But a still more extensive field of statesmanship was now opened to him. Canning had left the Foreign Office vacant; before the close of the year it was given to Lord Castlereagh. Another distinction followed. The unhappy assassination of Perceval left the premiership vacant; and Lord Castlereagh, though nominally under Lord Liverpool, virtually became, by his position in the House of Commons, prime minister.