London, England had local elections on May 1. As far as local elections go, the city has quite an interesting set-up.

The mayor is elected using the supplemental vote, which is a cruddy variant of IRV. Voters get two choices. If no candidate has a majority of first choices, the top two compete in an instant runoff of sorts.

All the other candidates are eliminated but the second choice votes on their ballot papers are reviewed. If they are for either of the top two candidates these votes are added to their totals.

The candidate with the most first and second choice votes wins. If there is a tie then the Greater London Returning Officer draws lots.

The 25-member assembly is elected under MMP: 14 seats in single-member plurality districts, 11 from party lists.

Some are upset that proportional representation let the British National Party win a seat, but that’s no reason to toss out the baby with the bath water. Undesirable causes can prevail under any voting system, and PR also lets forces for good win seats where they might not otherwise. As the Make Votes Count campaign notes:

However, the way the London Assembly elections work has also given anti-racist campaigners the opportunity to organise, campaign and get out the vote in their own areas, in an effort to push up turnout and raise the threshold needed for the BNP to gain seats. Anecdotal evidence suggests that the message that votes in the London Assembly London-wide Members ballot in effect counted twice – once for the party they support, and once against the BNP – motivated numbers of people who otherwise may not have voted to make the trip to their polling station.