Another train-based anecdote (or the Origins of the Zombie London Mayoral System)

Overheard a conversation between a group of girls on the train between London Euston and Stoke-on-Trent last Friday. Apparently the London mayoral election is conducted using proportional representation (rather than the supplementary vote system, as I previously understood). I can only assume this means that once the votes have been counted, chunks are hacked from each of the candidates based on the percentage of votes they have accumulated and stitched together to make a Mayor. Sounds awesome, right?! ZOMBIE MAYOR!!