Bertie Ahern's decision to relinquish office next month is the right one. An 11-year tenure is rather long by the standards of modern democracies and inevitably results in personal fatigue and political inertia. His authority has, furthermore, been compromised by the revelation that he accepted monetary support from friends while serving as Irish Finance Minister in the early 1990s. While few suspect him of outright corruption, the impression left that he was exposed to the influence of wealthy associates is not appealing. This saga has dominated domestic politics in Dublin for the past two years. It would have overshadowed the next two years too if he had continued. His resignation spares his country that spectacle.

Mr Ahern has served as Taoiseach for longer than anyone since Éamon de Valera, a former Fianna Fail Prime Minister. Apart from that, however, any comparison between the two men ends. De Valera was an intensely divisive figure within Ireland itself but especially between the South and Ulster and between Eire and the United Kingdom. His very long political career ossified Irish politics, with the split initiated by the civil war of the 1920s still dominating the system more than half a century later. He showed little interest in the continent of Europe and seemed to revel in the idea of Ireland's victim status.

This was a profoundly unsatisfactory situation. It is to Mr Ahern's immense credit that he has sought to accomplish the opposite ends in his period in power and has been largely successful in that endeavour. His inexhaustible patience and considerable courage allowed the Good Friday agreement and then its various added accords to be established. He sought a working relationship with the Rev Ian Paisley from the earliest stages of the peace process and the two men have reached a remarkable accommodation with each other. The notion that they could each invite the other to the parties marking their retirement from their respective posts either side of the border would have been laughable even a few years ago. Yet that is precisely what Mr Ahern's diplomacy has achieved.

The Ahern effect has, nonetheless, registered well beyond the peace process, an enormous triumph for him as it undoubtedly is. He has overseen Ireland's social and economic renewal. The single greatest indicator of this is that the population of the Emerald Isle is now increasing consistently for the first time since the Great Potato Famine. Although economic times have been tougher of late, the growth rate witnessed in the past 15 years has been extraordinary and Mr Ahern's acceptance of a low-tax, low-regulation formula has been a vital part of it. This again reflects well on his flexibility and pragmatism as his party has traditionally been comparatively statist in instinct.

It had also previously been associated with a deadening social conservatism. Under Mr Ahern, the charge that Ireland was a form of theocracy, often made in Ulster but not only there, has become implausible. Partly because of his private life (as a divorcé) but also through his public style, Mr Ahern has been a force for, and a symbol of, a new modernity. While the manner of his going is not as dignified as he would have wished, his legacy is an extremely positive one. The next Taoiseach, almost certainly Brian Cowen, will inherit a country that is considerably more confident about, and comfortable with, itself than when Mr Ahern was first elected. Not many politicians can depart knowing that.