Alternative Voting (AV) replaces the 'X' on our ballot papers with numbers. Voters rank candidates in order of preference, writing 1 in the box next to their favourite candidate, 2 next to their second choice and so on.

You can back as many or as few candidates as you like and you don't have to rank any candidate you wouldn't want representing you in Parliament.

Everyone's first preference votes are counted up and if a candidate has 50%, they are elected.

But if no-one gets 50% of the vote, the candidate with the fewest votes drops out.

Those who voted for the bottom-placed candidate as number 1 have their second-preference votes transferred to the candidate they ranked number 2.

If any candidate has now reached 50% of the vote, they are the winner.

If no-one is yet at 50%, the candidate with the fewest votes is eliminated.

Voters who chose that candidate as number 1 have their second-preference votes reallocated to the relevant remaining candidates.

Voters' second preferences only come into play when their first choice drops out.

If their second choice is also eliminated, their vote is transferred to any candidate they ranked at number 3. If that candidate also drops out, the vote is passed on to any number 4 choice and so on.

This elimination process continues until one candidate has 50 per cent of votes, which could be when just two candidates remain.