Leading article: Boris Johnson builds his legacy

When Boris Johnson was elected Mayor of London, many of his political opponents (even some of his admirers) predicted that his administration would soon self-destruct. Well, almost a year has now passed since Mr Johnson won the keys to City Hall and the Conservative Mayor has successfully defied such predictions.

But what achievements, aside from the avoidance of disaster, have there been? The most significant interventions of Mr Johnson have been in relation to the Metropolitan Police.

Mr Johnson effectively dismissed the former commissioner, Sir Ian Blair, last October. And in taking up his right to chair the Metropolitan Police Authority, he signalled his intention to make the force more accountable. The brutal policing of the recent G20 protests suggests that this new approach has yet to yield dividends, but it is hard to fault the Mayor's effort.

Another interesting feature of Mr Johnson's year in office has been his relations with the Conservative leadership. Along with his party, Mr Johnson opposed the Government over the third runway at Heathrow. But the Mayor has been much more outspoken than David Cameron in defence of London's banking community, widely blamed for the financial meltdown. He also took a stronger line than Mr Cameron in criticising the 50p tax levy for high earners announced in the Budget last week. Mr Johnson has also supported an amnesty for illegal immigrants.

These stances certainly make sense for the mayor of a city that has built its prosperity on the financial services industry and immigration. But they do suggest possible points of friction ahead if the Conservatives win the next general election.

Yet perhaps the real surprise of the past year is that that Mr Johnson has not shaped the political agenda to the extent that his hefty electoral mandate might have allowed him. To a large degree, he has ploughed on with an agenda inherited from Ken Livingstone, particularly regarding the 2012 Olympics. Indeed, Mr Johnson's political legacy could be heavily shaped by his delivery of these Games. If he continues to defy predictions of imminent meltdown, that legacy is on course to be a healthy one.