With apologies to Labour, the Liberal Democrats, SNP, Greens, nationalists and unionists, the UK is a strict two-party system. It is comprised of the Conservative Party and the Not Conservative Party.
A cursory glance at the last 100 years will tell you this generally works out pretty well for the Conservatives. The party has been in power in one way or another (majority, minority, coalition, national) for roughly two-thirds of the period.
