If you’re voting in London tomorrow, you are going to be given three ballot papers—one for the mayoralty, one for the constituency section of the London assembly and one for the proportional vote. In the mayoral vote, you can vote for a first preference—we’d recommend putting a tick next to Boris—and a second preference. If your first preference is Boris or Ken, then your second preference is irrelevant. But if you’re voting for one of the other candidates, your second preference is key. In reality, there’s not much point putting anyone other than one of the two leading candidates as your second preference as the votes will be reallocated between the two people who finish with the most first preferences votes. (Obviously, if one of Boris or Ken gets more than 50 percent of the first preference votes, second preferences won’t come into it.) In the other two ballots, you just vote for a candidate in the constituency section and a party in the general one as normal.