It's always possible that Mandelson will do a good job

For the first time, he has the chance to move out from the incestuous relationship he has enjoyed with Blair

As so often in Labour Party history, a parallel, however imperfect, is at hand. In 1977, the Labour MP for Ashfield, David Marquand, abandoned his seat for a cushy job in Brussels - working for the new European Commission President Roy Jenkins. Marquand, who later joined the Social Democrats, is these days a leading public intellectual who, like so many who helped to form that party, finds himself well to the left of Tony Blair. But back then, he was seen by many of his colleagues as a rabid right-winger.

As so often in Labour Party history, a parallel, however imperfect, is at hand. In 1977, the Labour MP for Ashfield, David Marquand, abandoned his seat for a cushy job in Brussels - working for the new European Commission President Roy Jenkins. Marquand, who later joined the Social Democrats, is these days a leading public intellectual who, like so many who helped to form that party, finds himself well to the left of Tony Blair. But back then, he was seen by many of his colleagues as a rabid right-winger.

The bitterness provoked by Marquand's departure was hugely compounded when Labour lost the seat in the subsequent by-election. When Jenkins, famous for his inability to pronounce the letter "r", made his farewell speech to Labour MPs saying that he left without any "wancour", Dennis Skinner reportedly interjected from the floor: "I thought you were taking Marquand with you".

The by-election loss of Peter Mandelson's seat in Hartlepool, if it happens, will hardly be the blow that the Ashfield defeat was to Jim Callaghan's wafer-thin majority. Conversely, however, Mandelson is a vastly more controversial - and relentlessly high-profile - figure within the Labour Party than ever Marquand was; hence the outpouring of outrage, genuine and synthetic, at what for virtually any other politician would not be much more than a mildly interesting appointment.

True, it is hard to think of a British figure who came back from the political dead twice. If nothing else, it is a testament to Blair's loyalty to his old friend that, having twice forced him out of the Cabinet - the first time for clear and entirely compelling reasons, the second time for reasons which were rather less so - he has now fulfilled his promise to restore him to public office.

I don't believe either Blair or Mandelson even contemplated his return to the Cabinet this side of an election. Rather, the delay seems to have arisen because, in offering him the Brussels job, Blair indicated that he woudn't mind if Mandelson refused it, accepting in its place a party role planning the next election after which, if everything went smoothly, even his many enemies would be reconciled to his return to the Cabinet in a third Labour term.

This was a tough call for Mandelson. On the one hand, by accepting Brussels he was leaving the House of Commons and a British political career, almost certainly for good. On the other, the conditional promise of yet another re-entry to the Cabinet was hardly bankable. And there were real attractions in leaving the Westminster hothouse. Moreover, Gordon Brown, the most dangerous Blair opponent in the Labour Party, would surely prefer Mr Mandelson to be at the far end of the Eurostar line.

But then the further you are from Westminster, the more striking it is how little the present debate takes into account the possibility that he might be rather good at the job, let alone that it might, therefore, be in British interests for him to go there. Experience makes it clear, to put it mildly, that every Mandelson appointment is risky; he could implode once again. And even if he doesn't, his mere presence in Brussels could be demonised in a referendum by the anti-Europeans as the epitome of everything they claim Europe to be: arrogant, élitist, out of touch.

On the other hand, there are serious advantages in having in Brussels a front-rank politician of ability - which not even his enemies deny - and one who actually believes in the European cause, as he has done consistently since his youth. Robin Cook would have been an outstanding candidate. But because of Cook's role as an honourable and persistent critic of Blair over Iraq, he was never going to be appointed. Whatever their other qualities, it's hard to see Geoff Hoon, or the Barronesses Scotland and Amos, in a top portfolio like trade or the single market; it's perfectly possible to see Mandelson in one.

As always with Mandelson, there is a gripping human story here He is lucky to have such a loyal friend. But perhaps for the first time in his career, he has the chance, in a job at least formally independent of the government of the day, to move out from the incestuous relationship he has long enjoyed with Blair, often to the detriment of both, to stop always being His Master's Voice and to show a little of the autonomy the best of our commissioners have done over the years. If he can conduct himself well - and, of course, it's a very big if - this will certainly be in his own interests. It may also be in the country's.

The writer is the author of 'Mandelson and the Making of New Labour'