CONSERVATIVES were today hoping to put the cherry on the cake of their overnight electoral victories by seizing the London mayoralty from Labour for the first time.

The scale of Tory success in local elections around England heightened speculation that Henley MP Boris Johnson may be on the point of snatching the crown in the capital from Labour's Ken Livingstone.

However, few in politics were certain results in the rest of the country could be directly translated to London, where the mayoral poll is a highly personalised contest whose winner has the biggest direct mandate of any UK politician.

Mr Livingstone has already proved in 2000 - when he ran as an independent - that his support is not dependent on Labour's popularity nationwide.

And Mr Johnson's high profile as an outspoken journalist, gaffe-prone shadow minister and sometime TV panel show host may prove a more important factor than his party affiliation in determining his share of the vote.

The race to run City Hall is the highest-profile contest in the 2008 round of elections, and its result could have a powerful impact on national politics in the run-up to the next general election.

Victory for Mr Johnson would add considerable momentum to Tory leader David Cameron's drive to win power nationally, and would make the former journalist the most powerful Conservative in Britain.

But if Mr Livingstone sees off the Tory challenge, it will provide a crumb of comfort to a bruised Gordon Brown after his pummelling in the local elections.

Polls have suggested the tightest result since the position of mayor was created in 2000.

The mayoral result is expected early in the evening.