Suppose you have 20 districts, each electing its own MP, and each with exactly four citizens. One citizen in each votes UKIP, one votes Labour, and two vote Con

Suppose you have 20 districts, each electing its own MP, and each with exactly four citizens. One citizen in each votes UKIP, one votes Labour, and two vote Conservative. Conservatives will win 20 seats, despite getting only 50% of the national vote, and the other parties will have none despite getting 25% each.