WE CONGRATULATE Tony Blair and New Labour on a quite exceptional victory. It is a magnificent, epoch-making achievement. Only five years ago, pundit after pundit was pronouncing that Labour was unelectable. Now it is the Tories who are looking unelectable, although we suspect they too will rise again from the ashes of despair and humiliation in which they find themselves today.

We salute New Labour's triumph. But it is neither grudging nor inappropriate to enter two crucial caveats. First, we have witnessed tactical voting on a colossal and hypersophisticated scale. The nation was basically voting the Tories out rather than New Labour in. The electorate used the much-maligned first-past-the-post system with devastating efficiency, but it is clear that despite the scale of the victory, Labour has not received an overwhelming endorsement. Indeed, the new Government received fewer votes than John Major's Government did in 1992, and its share of the vote is not much higher than that of the Tories in 1992.

Secondly, for an administration that has been elected in such an astounding, even cataclysmic, manner, it has to be said that its own agenda was almost defiantly unambitious. The New Labour manifesto was not only vague, as we complained on Wednesday: it was also very much a manifesto for small changes rather than major reforms. The irony is that the voters have produced what is almost a revolution when they were in effect being asked to exercise caution.

Now that Tony Blair is in a position of such sway he might be tempted to tear up his careful approach and espouse a radicalism that will surprise us all, including members of his own Cabinet. When Harold Wilson was elected in 1964 after 13 years of Tory rule, his first few months in office proved dismally unadventurous. But then he had a tiny majority; today, Tony Blair has no such alibi.

One of the new Prime Minister's favourite phrases is ''the radical centre''. Nobody is as yet quite sure what that means, but it is clear that both the right and the left have been marginalised by this extraordinary election result. There might be dangers in that - fringe fanatics can always take advantage of centripetal tendencies - but it could also be that we are seeing the start of new polity, and old labels like left and right will become redundant; maybe we in the press shall have to construct a new journalism to reflect the new politics which seem to be emerging. In any event, we are clearly in for exciting, not to say exhilarating, times.

Certainly, the much criticised British constitution has produced one of the most amazing results in any democracy anywhere this century; the voters used a tried and

not so trusted electoral system to deliver shock after shock, sensation upon sensation, as the results unfolded through the small hours of Friday morning. In the 15 short hours that the polling stations were open, these voters had taken the opportunity to map out an entirely new political landscape.

Mr Blair now dominates this landscape like some fresh-faced colossus, and his huge majority gives him much scope - quite possibly he has more sheer power at his disposal than any Premier since Winston Churchill in the desperately different circumstances of 1940 - though he may find it less easy to continue to exercise the remarkable discipline he and his lieutenants have thus far imposed on their party. He will also lack, in the Commons, the effective Opposition that can paradoxically be helpful to tyro Governments. As we noted earlier this week, the Tories had become a squalid rabble and there is no evidence that their vicious internecine strife will now cease. Indeed it might even be exacerbated as they are launched into a leadership struggle with almost undue haste.

In Scotland, the 17% who voted Tory are bereft of a single parliamentary representative. There is undoubtedly a democratic deficit here, but at the same time the fact that a Scottish parliament is now that much closer will surely alert the more sensible Tories to the possibilities for revival that that body will represent. It will be ironic indeed if a Scottish parliament delivered by Labour, with the praiseworthy support of the Liberal Democrats, proves to be the saving of the Tories north of the Border. Let us hope that the more imaginative Tories in Scotland - and there are some - have at long last the gumption to seize the opportunities offered by devolution; and let us also hope that the new Tory leader, whoever he may be, shows more understanding of the Scottish dimension in UK constitutional politics.

Meanwhile, even the millions of voters who did not vote for New Labour on Thursday must surely admit to a new zest in our national life, a new spirit of hope and aspiration, on this spring weekend. The election campaign was too long, too timid, and distinctly uninspiring. Yet out of it has come a sea-change. Our politics are entering a potentially momentous new phase. Mr Blair and his colleagues are seriously inexperienced and they have much to prove. But there is outstanding talent in his team, and many opponents of New Labour will be prepared to suspend whatever misgivings they may legitimately have, and give the new Government the benefit of the doubt at this period of great expectation.

Finally, it is only fair to commend the Tories, at their lowest ebb in a century and more, and so tainted by sleaze and squalor, for the decency and grace with which so many of their senior figures accepted both individual and collective defeat. Our system imposes change with brutal swiftness; it also allows for the display of dignity in exacting circumstances. We have seen much of that. We can reflect this morning that there is much for all of us - not just our politicians - to do, but there is much to be grateful for also.