Jim Hacker is England's Prime Minister. He does have some good ideas, but Sir Humphrey -- played by Nigel Hawthorne -- always makes sure that none of Jim's ideas are realized. Jim Hacker is a Tory, alright, but he is in fact more of a liberal man -- that keeps Sir Humphrey busy, who would do anything to keep the UK from adopting progressive politics. Of course, Jim himself does have some serious flaws himself, not so much on the political, but rather on the personal side -- this makes Sir Humphrey's "job" a lot easier.
Nigel Hawthorne spreads the same kind of Tory charm that he does in _Her Majesty Mrs Brown_, where he interprets D'Israeli. _Yes PM_ is for those who like a bit of politics and LOTS of humour: the eternal fight between progress (Jim, his wife, Dorothy) and reaction (Sir Humphrey and Bernard, Hacker's secretary, who's always driving the others mad with his speeches on Latin and Greek grammar...)
