The story may be old. But it loses none of its accuracy, or appeal, in the retelling.
Fresh from the rigours of an election campaign, the newly elected MP arrives at Westminster for the first time. Having sworn the oath, he takes his seat, and turns excitedly to a senior colleague. "This is great," he declares: "Now I can confront the enemy across the floor of the House.".
"My dear boy," replies the old hand. "Over there sit the Opposition. The enemy is on this side.".
Tony Blair will know the truth of it better than most. The Prime Minister, we are told, grew somewhat alarmed on the night of May 1st, 1997, as the scale of his electoral triumph became clear. His immediate fear may have been the impact of New Labour's massive majority on his project for a realignment in British politics.
He may, more generally, have been reflecting on the wisdom of Francis Pym's warning about the dangers of big majorities on the eve of Margaret Thatcher's victory some 10 years before. Thatcher never forgave Pym. But he was right.
The government's business managers have done their best to keep underemployed backbenchers occupied. For one week in the month swathes of them are dispatched to their constituencies to nurse their local electorates. But with the Tories still nowhere, the sense grows that the opposition to this government is still most likely to come from within its own ranks.
Ironically, and perhaps inevitably, that danger is nowhere more apparent than in relation to the government's flagship programme of constitutional reform.
Leave aside the proposed devolution to Stormont. Ministers occasionally remember to link reference to the component parts of the United Kingdom. But for the most part they discuss devolution, and consider it, in the context of a debate about the future of Britain. And in Britain all three big devolution projects, to Edinburgh, Cardiff and London, are already running into trouble.
At one level, technical and procedural, everything is coming together nicely enough. The legislation passed, Scotland and Wales will go to the polls on May 6th. Although still more than a year away, the race for the capital's top job is already joined. But we can already see, at least from the perspective of New Labour and No 10, how the whole thing might eventually come apart.
Longer term there remains the potential, still not convincingly addressed by government, for conflict between the devolved institutions and Westminster. But the immediate battles are being, and will be, fought within the ranks of New Labour; begging, in the process, questions about precisely what New Labour is, and, more crucially, how far Mr Blair's modernising tendency has taken hold in his party at large.
Blair's distrust of his party's Old Labour leanings has been manifest in Scotland, where the exclusion of prominent left-wingers like Dennis Canavan as candidates for the Scottish parliament has left a legacy of bitterness.
It is evident in Wales, where the leadership vacated by Ron Davies will be determined on Saturday week. Close observers say it is still possible for Rhodri Morgan to win against Mr Blair's nominee, the Welsh Secretary, Alun Michael. It will be a crushing blow to Mr Blair if he does. If he doesn't, we may witness the extraordinary spectacle of Mr Michael claiming the leadership courtesy of the trade union block votes, and without winning a single ballot, where they have been held, on the basis of one-member-one-vote.
There is also the possibility that, if Labour does extremely well, Mr Michael - who is counting on entry to the Welsh assembly courtesy of the party top-up list, rather than election in a constituency contest - might not actually make it, so forcing a third contest for the Welsh leadership.
But the most eye-catching battle between Old Labour and New is that gathering around Ken Livingstone's determined effort to be allowed to be his party's candidate for London mayor.
The former GLC leader came on all soft and cuddly the other week, telling Mr Blair he would be on his best behaviour; would not use what might become the second most powerful elected post in the country as a platform from which to attack the government; promising, even, to take a Blairite-like broadcaster, Trevor Philips, on board as his "dream ticket" running-mate.
Faced with Mr Blair's implacable opposition, Mr Livingstone this week started an all-out public campaign to force the leadership to permit him to put his claim before the party's 70,000 London members.
On the eve of the Welsh decision, a massive "Back Ken" rally will be held at Central Hall, Westminster, next Thursday, demanding that he at least be allowed to be a candidate for the party's nomination.
It isn't hard to understand Mr Blair's reluctance. Livingstone as mayor would be a permanent footnote to New Labour, a powerful reminder of what Labour was pre-Blair (and doubtless, in many areas, remains despite him).
But can Mr Blair have it both ways, willing to devolve powers to countries and regions, but not to regional and local Labour parties? If he so lacks confidence in the people's verdicts, was he wise to embark on the whole enterprise in the first place?
There have always been doubts about the basis on which Mr Blair committed himself to the devolution project in the aftermath of John Smith's death. The tension between declared policy and personal instinct were laid bare when he enraged Scots during the 1997 campaign, appearing to liken the proposed fiscal powers of the Scottish parliament to those of a parish council.
And the vision of a still-all-powerful London-based establishment clearly holds little appeal to people like Ron Davies, who last week warned that devolution should be seen as "a process" rather than "an event".
For the real devolutionists, one fancies, that is exactly the point.
And not even Mr Blair can hope to determine its end result.