In the UK the Prime Minister doesn’t run the Country. He or she is not some sort of dictator, controlling all the levers of power including the Military. No, he or she is only the Leader of the government for as long as their particular party determine, or the House of Commons decide otherwise (by ‘defeating’ the government).
Prime Ministers come and go – that is the nature of politics. Most go actually because the public decide and vote their party out of power; some do go though because their own MPs lose faith in them – you don’t have to be all that knowledgeable or cynical to realise that MPs get rid of their PM solely because they think that are going to lose their own seat at the next election, and hope that some newcomer will save their bacon.
No one knows in advance if a particular PM will be ‘up to the job’ – it’s a matter of suck it and see. David Cameron our Conservative PM is currently accused by many of not being up to the job – well you’ve guessed it; his MPs are running scared about the General Election in 2015! Well, we will have to wait and see how he gets on – something big might happen to him (PM Margaret Thatcher was on very thin ice and on the verge of outage, when she got saved by starting (and winning) a war with Argentina over the faraway Falkland Islands (a conflict which incidentally was her fault anyway).
Who in the recent past half century is possibly seen as deficient?
Antony Eden Conservative 1955-57 – got found out by the Suez crisis
Alec Douglas-Home Conservative 1963-4 –renounced his Peerage to get the job but harmed by the Profumo sex scandal and his aristocratic image
Edward Heath Conservative 1970-74 – undone by the 3-day week and misreading the will of the electorate
John Major Conservative 1990-97 – despite winning was seen as a loser (the grey man)
Gordon Brown Labour 2007 -10 – lacked charisma and the courage to go to the electorate at the appropriate time
[or who do you think should be in the list?]