1. Blair
2. Cameron
3. Boris
4. May
5. Brown
Why is Brown last?
He handled the recession terribly
now that's a hot take: you could make a decent case that his handling of the recession was the best part of his career. His popularity nosedived during 2008 due to his backflip about calling an early election and the 10p tax credit, and actually rose during the crisis itself, only to fall again during the expenses scandal and the flare-up of Blairite resentments (he also suffered some kind of mental break in power)