WHEN Londoners go to the polls on Thursday next week, they will have a chance to vote in three different elections, for the Mayor of London, the London Assembly and the European Parliament.

June 10 has been dubbed Big Thursday, a reference to Big Tuesday in America when a large number of presidential primaries are run simultaneously.

The local elections in London and across the country should have been held in May, but the Government passed a law allowing them to be postponed for a month to coincide with the Euro-elections.

This was, in part, a streamlining exercise, allowing those who organise and run polling days and counts to get everything done in one go, rather than having to repeat the exercise within a short time, but also a bid to increase the turnouts in two kinds of elections which traditionally have been met with a great deal of apathy among electors.

Turnouts in local elections have been falling steadily for years, and the Euro elections stir even less interest.

Many argue that it is pointless voting for a body which is, essentially, a powerless talking shop which can do little, if anything, to control or even influence the effect that the powerful eurocracy has on our lives.

So, when those who do think it worth voting next week go to the polling station, or receive the paperwork for a postal vote, they will be handed three ballot papers.

But it will not be just a case of putting your X in a box on each. For the three elections are being run to three totally different sets of rules, bearing little, if any, relation to the way in which English elections have been run for decades.

There might be three elections, but we have five votes.

European Parliament: one vote This is the simplest election, but it is very different to how general or borough elections are run. We each have one vote, but we are not being asked to elect a local representative to the parliament in Brussels and Strasbourg: at least not directly, and not very local.

Harrow and Brent used to be part of the NW London Euro constituency, which also included the borough of Hillingdon and which was represented at the Euro parliament by Robert Evans.

But in the Euro election of 1999, the Government abolished the Euro constituencies and removed the voters' right to choose an individual candidate. Instead, London was treated as one giant electoral region (bigger by population than some member states of the EU) with a team of ten Euro MPs.

We could vote only for a party. The parties were then allocated seats based on a form of proportional representation and then decided privately who, from a list of "candidates", filled those seats.

London's team of Euro MPs comprised five Conservative, three Labour, one Liberal Democrat and one Green. Mr Evans was re-elected, but no longer has a direct link to his old constituency.

This time, the voting system is the same, but London's team of Euro MPs has been reduced to nine.

Mayor of London: two votes The election of the Mayor will be by the "supplementary vote" system, under which we are asked to indicate our first and second choice of candidate, although you don't have to use your second vote.

If a candidate secures more than half of the first choice votes cast he or she is elected, and the process stops there.

But if, as is almost certain, no candidate passes this threshold, all the candidates, except those with the largest and second largest number of first choices votes is eliminated.

The second choice votes from all of the eliminated candidates are then added up and distributed and the candidate from the remaining two with the biggest combined total of first and second choice votes is elected.

Should there be a tie, the Greater London Returning Officer will draw lots. No matter how close the result, the law does not allow a recount.

London Assembly: two votes The London Assembly election combines the traditional English first-past-the-post system and a form of proportional representation.

The assembly has 25 members, but only 14 are elected to directly represent a constituency, such as Brent and Harrow. The other 11 are London-wide "top-up candidates" who provide the proportionality.

The voter is asked to choose a constituency member, with the candidate getting most votes winning, as in a general or borough election, and then to vote for a party, or independent candidate, to fill the London-wide seats.

Top-up seats are allocated pro rata to parties or candidates achieving over five per cent of the votes cast.

For more information, call the London Elects helpline on 0800 328 0280.