Actually Tinkleflower that is not true.
The 'line of succession' (such quaint odd Royalist terminology for a democratic process!) is found in the proceedures that exist within the
political party that the PM leads and is from and the method for selecting a new party leader that they have.
We have a parliamentary system in the UK, we elect a party to gov, despite the appearances we don't specifically elect a Prime Minsiter.
Look back to the time when British Prime Minister Harold Wilson voluntarily resigned and stepped down mid-term in the 1976.
or when PM Maggie Thatcher was actually ousted by the tory party she led in 1990
If the British PM resigned, died or was otherwise rendered incapable of performing the job the proceedure(s) would be entirely those of the political
party in government (with a little of our patent Royal razzamatazz thrown in).
It would be for the political party to select a new leader, that new leader would then become (after the swift formality of a visit to Buch. house to
see Queen or King) PM.
Whether or not the situation was such that the PM & party decided to go to the people in a new general election would be entirely a matter for them,
but there is no requirement, they would not 'have
(as happened with both Jim Callaghan - Harold Wilson's successor - or John Major - Maggie Thatcher's successor.
One might argue that not going to the people for electoral 'legitimacy' straight away didn't help either in the long run, but it's probably not
In the event that the parties were in coalition or so closely matched already as to be unable to agree the appointment of a new PM when the old one
was 'lost' then the Monarch is supposed to ask the leader of the biggest party if they can form a new gov, if not there most likely would then be
In the direst national emergency it's technically possible that the Monarch might try and just appoint a new PM or, even more unlikely, be asked by
Parliament to step in and appoint one but that is so enormously unlikely - I really can't think of it ever happening.
[edit on 21-9-2005 by sminkeypinkey]