All political analysis should be dynamic, rather than static. It is no use taking last Thursday’s election results and trying to calculate what they might mean at a hypothetical general election. Very probably, the next general election is still three years away, in a different age and a different world. Politics constantly changes and renews itself. These election results tell us something about the direction and speed of change; that is all, but it is enough.

In the South West, where I was following the local results, the most striking trend was the virtual disappearance of the Labour Party. There are now 109 councils in England which either have only a single Labour councillor or – most of them – none at all. Four of these are in South or West Somerset; in a large number of our local Somerset wards, there was no Labour candidate.

In England, Labour lost more than a quarter of its council seats; it is now in third place, 300 behind the Liberal Democrats, who are 3,000 behind the Conservatives. In Wales, Labour had its lowest share of the vote in almost 90 years, according to the analysis of Colin Rallings and Michael Thrasher, of the University of Plymouth.

In Scotland, Labour was defeated by the SNP in votes and seats, if only by a single seat. That is its worst result in Scotland since Anthony Eden was Prime Minister, and Alex Salmond is likely to prove a more dangerous adversary than Eden. Scotland used to be Labour’s biggest single asset; it is now Labour’s gravest constitutional problem.

Tony Blair is expected to announce the date of his retirement this week, so it is natural to look back on his ten years in office. No Prime Minister in my lifetime has had the same “glad, confident morning” as when he came into office after 18 years of Conservative government. To gauge the momentum of Labour’s decline, one can measure it election by election: the glory of 1997 was still very high in 2001, was beginning to decline in 2005 and was then followed by the disastrous elections of 2006 and 2007. The latest election has been bad in England, but potentially deadly in Scotland.

After too long a period in office, parties invariably go into decline. After 14 years the Conservatives were exhausted as a party in 1945, as they were again in 1964 after 13 years, and again in 1997 after 18 years. The most plausible date for the next election is May 2010, by which time Labour will have been in power for 13 years. In 1964, when Harold Wilson won the election, Labour was able to use the slogan “13 wasted years” against the Conservatives.

In the early 1960s, when the Conservatives were in trouble, Rab Butler, who had been the real architect of their postwar recovery, used to rally the troops by telling them: “We must maintain the momentum.” Even then, that seemed impossible, because the momentum had already been lost. Gordon Brown now has the unenviable task of trying to restore Labour’s momentum. Politics has been compared with a yo-yo. So long as it is in action, recovery is possible, but it cannot be kept in motion once it has dropped to the end of the string.

These elections show that Labour has now lost credibility in southern England and, in a different way, in Scotland. Unless Mr Brown can reanimate his party, Labour will have little hope of winning the next election. His task may not be possible. The momentum has moved to the Conservatives in England and to the SNP in Scotland. Both parties represent national aspirations; both are skilfully led. Some people may have been hanging back in recognising how effective a leader David Cameron has proved.

If one allows for Winston Churchill’s age in 1945, and his penchant for writing history, Cameron is probably the most popular Conservative leader of an Opposition since Benjamin Disraeli. He is certainly more popular than Balfour, Bonar Law, Baldwin, Heath, Margaret Thatcher before she got office, William Hague, Iain Duncan Smith or Michael Howard. More importantly, Mr Cameron operates on the basis of a consistent strategy. He has detoxified his party’s image and broadened its appeal. He is not only the best Conservative leader his party has got, he is the best Liberal leader as well. He is adept at stealing the clothes of his opponents.

Alex Salmond, the leader of the SNP, is a most formidable leader of his nationalist party. He knows how to woo the Scottish electorate; he, too operates as a strategist. He now has a golden opportunity before him. If he gets into office, he can use the Scottish Executive machine to bewitch, bother and bewilder a dying Labour Government in London. If the Lib Dems refuse to support him into office, he can complain about a conspiracy to keep out the SNP. A Scottish Executive that excludes the SNP will be a perfect target.

Mr Brown has been a strong Chancellor, though I am not sure that he will prove an equally effective party leader. He will face two exceptionally gifted party leaders. Mr Blair, at his peak, might have been able to handle both of them. I am not sure that Mr Brown can.

There are great dangers; we may be seeing the breakdown of the two-party system and perhaps of the United Kingdom. More than anything else, the fashionable adoption of proportional systems has undermined the old electoral system. We are now seeing a variegated, two-party system – Conservatives and Lib Dems in the South and South West of England, Labour and Conservative in the Midlands and part of the North, Labour and Lib Dem in Hull and Sheffield, Labour and SNP in Scotland, and a four-party system in Wales. This hotchpotch of different electoral patterns may make Britain ungovernable. If so, Labour will be the first to pay the price, but we shall all pay a price in the end.

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