January. A beleaguered Commission is on its last legs, battered by criticism from Parliament. Decisions are on hold, particularly appointments to senior jobs. All but one. Someone is needed to take the helm in DGXX11, the directorate for education and training and the fiefdom of the embattled French Commissioner, Edith Cresson.

Her outgoing Irish director general, Tom O'Dwyer, with whom she fell out some time ago, is retiring. The directorate is under fire from MEPs and the press over irregular contracts under the Leonardo programme . . .

It is an "Irish" job and David O'Sullivan's appointment to the thankless task of putting order on DGXX11 came as a surprise to no one in Brussels, but was remarkable nonetheless. The 46-year-old Dubliner had risen through the ranks of the Commission to become Ireland's most senior EU official faster than any before him.

Now, only a few months on, he has been plucked from the Commission services to act as the chef de cabinet of the Commission President-designate, Romano Prodi.

The job is critically important: the fixer who must chair the key weekly meetings that set the agenda for every Commission meeting, the broker of deals, the eyes and ears of the president inside the services, in other cabinets and with the member-states, the desk across which every piece of paper must move. Adviser and administrator.

Mr Prodi's decision to pick a non-Italian has been widely welcomed as a sign of his reforming intent and determination to be beholden to no one. Insiders say that in picking Mr O'Sullivan, he has also got someone who has shown he has the capacity to do the job.

Joe Brosnan, Padraig Flynn's chef de cabinet, pays warm tribute to his former deputy. He says Mr O'Sullivan knows the Commission inside out and has the toughness, adaptability and political sense required. Another former cabinet colleague, Barbara Nolan, also insists "he made his own luck".

In his time in the Flynn cabinet, Mr O'Sullivan played a key role in developing the Commissioner's flagship employment strategy and in fighting the corner in the Commission of social policy now that its champion, Jacques Delors, has moved on. He even unsuccessfully, only half seriously, once tried to write a quote from Marx into one of Mr Flynn's speeches. "Ah no, David," said Mr Flynn.

Mr O'Sullivan is in many ways the archetypal Eurocrat - in the best sense. Fluent in French and German, with passable Spanish and Japanese (and Irish, he says) he is a graduate of the College of Europe in Bruges who networks across the Commission's many nationalities with an ease that many Irish still find difficult.

Friends who remember him from Trinity days in the mid-1970s speak of a serious student who sometimes gave the impression of being a bit aloof, perhaps reflecting the natural reserve of an only son. His father is the former Chief of Staff of the Defence Forces, Lieut Gen Gerry O'Sullivan DSM, and Mr Brosnan sees in him, too, the inner quiet strength of a soldier. A student of economics and sociology, he avoided involvement in the highly-charged student or national politics of the time but he was a passionate and successful debater whose speeches clearly reflected deeply held liberal and moderate left of centre views.

He was elected auditor of the university's debating society, the Hist, a couple of years after Declan Kiberd and a couple before Mary Harney. George Birmingham, the barrister and former Fine Gael minister, says he was the "outstanding debater of his generation" and particularly remembers a packed Middle East debate at which Mr O'Sullivan's trenchant critique of Israeli policy was met by a standing ovation - from an audience full of members of the Dublin Jewish community.

And, late at night with friends, he is still wont to play the same songs on his guitar that he did then . . . "brought my Chevy to the levee, but the levee was dry . . ." "I haven't had time to learn new stuff," he says. "I'm a bit stuck in a time warp."

But music is still his passion and the best vehicle for relaxation. "I was brought up on classical by my mother, but in my mid-teens I got hooked on rock 'n' roll and never looked back."

His reading is, perforce, episodic - thrillers on holidays in Italy or on the ski slopes, Patricia Cornwell and Michael Conneally most recently - but he still tries to keep going to the cinema, his other great passion. Not a natural athlete, he has taken in recent years, however, to the gym, and plays some tennis. He admits to a fascination with politics, both its mechanics and policy, "but my views are too eclectic for me to ever have fitted in to a single party." And although a strong advocate of Europe's social dimension, he is quick to stress the need to balance that with an understanding of the needs of the wealth-creating sector.

He sees the recent Commission resignation crisis as an opportunity for a new start and a coming of age for both Parliament and Commission, an important re-balancing of relationships that will rightly give more power to MEPs.

But he admits to dismay at the perceptions the crisis has engendered in the public, "the impression of being badly served by an incompetent and corrupt administration. That is absolutely not the reality." One of the key challenges of the new Commission will be to redress such misconceptions.

Has he ever thought of coming home? Like many others, he admits, when he came first to the Commission in 1979 he expected to stay for only a couple of years and then return to the Department of Foreign Affairs, where he had been working.

"But I just kept moving on in the Commission - that was my choice, but I also think that it reflected the extent to which the civil service was open to people moving back and forward between Brussels and Dublin. Greater permeability between the two services needs to be encouraged."

He confesses to concerns about the effect of the new job on a family life that had only just begun to recover from the heavy demands of cabinet work. His wife, Agnes O'Hare, is a working architect who made few bones about her delight at the prospect of seeing more of him when he returned from the Flynn cabinet two years ago to the Commission's services. But she and their two children, Shane (8) and Kate (5), will be Commission widows once more.

Highly recommended to Mr Prodi by the latter's close friend, the former Irish Commissioner, Peter Sutherland, Mr O'Sullivan's other erstwhile cabinet boss, Mr Flynn, is no less unstinting in his praise. Congratulating him yesterday on his appointment, Mr Flynn said that his "meteoric rise in the European civil service is well deserved."

Mr O'Sullivan is a "complete professional with enormous competence," Mr Flynn said, "who will do Ireland and Europe proud."