Perceval (1762-1812) took office in difficult circumstances. The war was going badly with the Walcheren expedition a notable blot on the government’s record, while the dissensions of the Portland ministry followed by the notorious duel had deprived him of the services of Canning and Castlereagh (1769-1822). Despite the big majority Portland had won in 1807, enough groups had split from the government that it was not expected to survive the 1810 session. On top of that, the King descended finally into insanity in late 1810, and the Prince Regent was thought likely to bring in the Whigs.
Perceval turned this around. He had Liverpool’s help at the war ministry, and Wellington’s in the Peninsula, but his own strong economic management (he had been Chancellor of the Exchequer since 1807) and Commons mastery were also major sources of strength. In 1811 he easily survived the change to the Prince Regent, then in early 1812 he strengthened his ministry further by bringing in Castlereagh and Sidmouth, adding to both the government’s talent and its Commons support. By the time of his assassination, Perceval’s government was as strong as any since Pitt’s long first Ministry.
If he had lived, Perceval would probably have ranked Top Ten (he lacked Liverpool’s economic sophistication and overall flexibility, so might have lost office in the difficult post-war years). Even with only 2½ years in office, he should comfortably rank in the top 20.