Graphic: how the battle was fought | What the candidates stand for

Boris Johnson will remain an Oxfordshire MP for up to a year if he becomes Mayor of London in the closest race since the post was created in 2000. As 5.5 million registered voters prepare to cast their votes today, Mr Johnson’s constituency said that it did not expect to replace him as MP for Henley immediately.

With polls and betting markets on a knife-edge, Ken Livingstone and Mr Johnson will make a final push today to motivate their supporters to go to the polling station in an election at which the turnout is expected to be the decisive factor. Mr Johnson will spend a second morning at a key commuter station while Mr Livingstone will visit East and North London, rein-forcing the impression that the mayoral election has been a battle between a Labour inner London and Conservative suburbs.

Brian Paddick, the Liberal Democrat candidate, whose second preferences could prove decisive, will vote in Vauxhall, where he lives, then visit his party’s strongholds such as Richmond, Ealing, Brent and Islington. His campaign predicts he will get more than 15 per cent of the vote.

Rain is expected over London for much of the day, making the turnout battle more difficult for the hordes of volunteers who will be helping the candidates. Elections are also being held for the 25 London Assembly seats, amid fears they could provide a platform for a BNP breakthrough. Its share of the vote could rise above 8 per cent, and it could win two seats after an aggressive campaign in parts of East and North London.

Mr Johnson’s campaign has been boosted by a late surge in donations during the final months, with the Tory coffers taking nearly £140,000 in March, almost double February’s £74,000. The most recent funding included £50,000 from Harris Ventures, whose chairman is Lord Harris of Peckham, a wealthy Tory donor. Another £10,000 came from Jonathan Marland, who is expected to be one of Mr Johnson’s City Hall advisers if he wins. Mr Johnson’s father, Stanley Johnson, gave £1,100.

It is not possible to compare Mr Johnson’s funding tally with those of his Labour rival, as the mayor does not publish his individually. Despite Tory complaints, Mr Livingstone’s campaign maintains that his donations are made to the Labour Party and therefore need only be declared as such.

Mr Johnson could face a large drop in income if he is elected mayor, even though the holder of the office commands a salary of £137,579. According to his entry in the Register of Members’ Interests, he earned about £250,000 for a weekly column in The Daily Telegraph, up to £75,000 for speaking engagements and up to £40,000 for book contracts, as well as £35,000 for television programmes.

A Tory campaign source said that he had not made any commitment to give up his Telegraph column for certain even if he become mayor. However, Mr Johnson will apparently continue as an MP for Henley in addition to his work at City Hall if he wins.

John Walsh, the Conservative agent in Henley, said that the local association would be looking for a candidate “in an orderly fashion”. He added: “This will not be done in a rush. We have a timetable to select a candidate before the summer holiday, with a potential for an autumn or spring by-election.”

The mayoral election is being conducted using the supplementary vote system, with every Londoner getting two votes for mayor, and the result could be decided on second preferences. Mr Livingstone is casting his second preference for Sian Berry, the Green candidate. Tomorrow Mr Paddick will reveal the name of the candidate who will have gained his second preference vote. He has maintained a careful balance between the main two contenders for the duration of the campaign.

Counting will not begin at four centres until tomorrow morning, with the result announced at City Hall probably between 5pm and 7pm. This could be delayed further if recounts are demanded.

Tonight will mark the end of Mr Johnson’s self-imposed alcohol ban, which began last autumn when he declared his candidacy. Campaign staff say that he has not broken the restriction except for a “couple of glasses of wine” at Christmas. The gap between the close of polling and the announcement of the result means that Mr Johnson will continue to be in the spotlight even after his campaign is over. The Times has been told there are plans for two parties, one for his close campaign staff who have been working at County Hall under Lynton Cros-by, followed by a larger party near by for supporters.

The winner takes over 48 hours after the final constituency has been declared, meaning that a new mayor would take the reins on Sunday evening. Among the first tasks will be to meet London Olympic chiefs.

Poll points

— Elections are taking place today for the Mayor of London and Greater London Assembly, plus almost 4,000 council seats across 137 English and 22 Welsh councils

— In England, 36 Metropolitan boroughs, 19 unitary authorities and 67 shire districts will each hold elections for a third of their seats, which were last contested in 2004

— Seven further English shire districts are contesting half their seats, and four shire districts are holding all-out elections because of boundary changes

— There are four new English unitary authorities that have been created by changes in council structure - East Cheshire, Chester and West Cheshire, Northumberland and Co Durham - in which every seat will be fought, and 22 Welsh unitary authorities, which are also all-out

— In the contest to be London Mayor, which uses a supplementary vote system, each voter has two votes. If no candidate has an overall majority on the basis of first preference votes, all candidates except the top two - Ken Livingstone and Boris Johnson barring a dramatic upset - will be knocked out. The second preferences of their supporters will then be redistributed

— In the GLA elections, voters will pick the winners of 14 constituency seats, which are made up of combinations of London boroughs. A further 11 seats will be distributed between the parties based on the result of London-wide vote

— The number of people registered to vote has risen to a record 46 million before these elections, with 500,000 signing up in the past year

— More than two million people are expected to vote by post, including at least 700,000 of London’s 5.5 million electors

— Approximately 100 Welsh councillors have already been returned because by the close of nominations no one was standing against them

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