That was the week, that was, that the ruling class threw in the towel. No, not in Albania. In Westminster, the City, the Home Counties and beyond. It took a few days for the import of the Wirral South by-election to sink in, but now the Tory power elite has given up.

We record the visible signs on our news pages today. Edwina Currie talking yesterday of the "formation of columns and lines and factions and groups" in the leadership election which she wants to see as quickly as possible after defeat. The Tory columnists Matthew Parris and Boris Johnson writing about the certainty of defeat in The Times and The Telegraph. But there is a less visible change happening, which is difficult for daily or even weekly newspapers to record. It is the intangible shift of power from one community of government to another. This is the week to stand back, observe and wonder.

A community of government is a large body: much broader than simply ministers or MPs. There is a hinterland of influence-brokers around a government, irrigated by the flow of power. And beyond them, a whole social stratum which draws sustenance from the same source. For the middle classes of the Home Counties, bound together by complex, overlapping subgroups of company directors, financial traders, quango members, this has been "their" government. For 18 years, the public debate that mattered took place between rival sub-groups of this elite: between, for example, bicycling, tweed- jacketed Spectator fogeys and brash, pointy-lapelled Thatcherite businessmen.

For some time, power has been ebbing away from the Tory elite, but it is only this week that the tap was finally turned off. Suddenly, the Tory commentators find themselves on the outside, on the fringes of power. When they drink with Tory MPs, they are no longer drinking at the well of power. This week, they have started to realise that they no longer know what is going on. The people who will make the running are no longer their friends. They do not know the people who matter.

The cynic may be prompted to ask: so what? Has Tony Blair's success not been to build bridges to precisely those social groups that sustained the Tories in power? The whole point about the coming election, surely, is that nothing is going to change.

But this is a fundamental misreading of the nature of political change. If Mr Blair wins, the personnel of the power elite will change completely. It is hard to over-estimate the impact, if he really does win, that this will have.

As the Chancellor put it yesterday: "There is no option marked `Tory Policies, Labour Men'." The new power elite is made up of Labour Men and Labour Women, and although they may start by accepting many Tory Policies, they will operate them on Labour Assumptions.

In part, this is a generational shift: the new elite will be younger, it will speak a different language, it will care about different things. For example, the new guard will not give a moment's thought to fogeyish Tory reservations about constitutional change. For them, the only objections to reform are the practical ones of rival priorities, rival models of democracy and arguments of efficiency. For another example, imagine the pressures on Gordon Brown as he draws up his first full Budget. Of course, much of his room for manoeuvre would be constrained by the same factors that would limit Kenneth Clarke - which the shadow Chancellor has explicitly acknowledged by accepting in advance some of the key Tory tax-and-spend figures. But there will be a host of other decisions to be taken, many of which could be or become just as important as the top rate of income tax. It is possible - to put it no higher - that the networks surrounding Mr Brown will instinctively take a different view of green taxes, equality (a word that might cease sounding old-fashioned) and welfare dependency.

Much of this is difficult to predict in advance. Margaret Thatcher did not know in 1979 what Thatcherism would be like. The feel of Conservatism has changed several times over the past 18 years. It was fought over by economic liberals and social authoritarians, moulded by the practical need to sell off state assets, and twisted by the gravitational pull of European integration. It is probable that not even Mr Blair knows in 1997 what Blairism will be like. Its meaning will be contested both within new Labour and between new Labour and old. Many of the Labour power elite are northern, even Scottish. Many come from trade-union and left-wing backgrounds, even if they hold modernised views. They are likely to clash with the new power brokers moving in towards the centre of power in the business world.

Some of this change could mean the replacement of one clique of cronies and courtiers by another. This newspaper drew attention this week to the empire-building tendencies of the shadow Chancellor, which are ominous for a Blair administration. We have also been sceptical about Mr Blair's relations with some multinational corporations, such as NewsCorp and BT. The character of the new groups to which power shifts will, in the end, depend on the character of Mr Blair.

On balance, this change is likely to turn out to be refreshing. The renewal that is possible if the rivers of power flow into fresh channels should confound the cynics who fear that the election will change nothing. The election may still be a month and a half away, but this week saw the beginning of a big change in the culture and character of British politics. Suddenly, Conservative camp followers are finding out what life is like when you are no longer inside the tent - plainly a humbling experience, particularly for those who have never known any different. But at least we know it will be good for them.