Londoners went to the polls on Thursday to choose the city's mayor in one of many elections taking place across the country.

The London mayoral election sees a field of seven candidates compete for the post, elected by 5.8 million voters.

The two leading contenders for London mayor are present incumbent, the right-wing Conservative party's Boris Johnson, and the first London mayor Ken Livingstone, the left-wing Labor Party's candidate who has won the mayoral election twice before and served eight years in the job.

An opinion poll by polling organization YouGov for London's Evening Standard newspaper predicted that Johnson would win, taking 53 percent of the vote against Livingstone's 47 percent.

Voters will use the supplementary vote system, voting for a first preference and a second preference candidate. The post lasts four years, and is not to be confused with the ceremonial Lord Mayor of London who represents the small area that is the historic core of London, and who holds the post for just one year.

The result will not officially be confirmed until late on Friday evening, with the London election authorities busy counting votes for the mayor and the mayor's London Assembly -- in total three elections, each using a different system and a different ballot paper.

Exit polls are likely to give an accurate indication when poll close at 10 p.m. London time.

Tony Travers, the director of the LSE's Greater London Group, said, "Johnson is polling well head of the Conservative Party, and Livingstone well behind the Labor Party. There is no question that on national voting Labor have a lead, but in the mayoral election, Johnson has a lead. That's an extraordinary defiance of political gravity."

At the same time as London goes to the polls to choose a mayor, which looks likely to deliver a victory for Prime Minister David Cameron's Conservative Party, municipal elections are being held across England, Scotland and Wales, using a variety of different electoral systems in which 30 million voters will choose 5,000 local councillors.

These were described by Travers as an "increasingly important set of mid-term elections." Where Johnson and the Conservatives look likely to do well in London, and his Conservatives are likely to do badly across the country.

A poll in a national newspaper on Tuesday showed Labor has opened up a 7-point lead in the polls, on 40 percent to the Conservatives' 33 percent. Coalition partners the Liberal Democrats are set to do badly, down on 11 percent, compared with 23 percent the last time these seats were fought for in 2008.

These elections last took place in 2008. The then national government was an unpopular Labor administration, and it did badly at the polls, with the the then-opposition Conservatives doing well.

The situation is reversed this time.

Labors look set to take control of several English cities from the Conservatives, notably Plymouth and Reading.

In the English Midlands, the largest municipal authority is Birmingham, currently controlled by a Conservative/Liberal Democrat coalition that looks certain to be defeated by Labor.

Turnout looked to be low, about 35 to 40 percent, said Travers, but it was always at that level for local elections and was not in decline.

"The decline is in general elections," said Travers, where voters show their disillusionment with party politics.

Elections are taking place in 36 metropolitan districts, across England, as well as in 74 shire counties and 18 unitary authorities.

In Wales, 22 districts will see elections, and in Scotland a total of 32 districts.

There will also be referenda on whether to have a mayor or not in 10 English cities including Bristol, Birmingham, Manchester, and Newcastle upon Tyne.

Full mayoral elections will take place for the first time ever in Liverpool and Salford, both cities in the north of England.