How unusual is the United Kingdom Coalition (and what are the chances of it happening again)?

This article draws upon insights from theoretical and empirical studies of coalition behaviour in multiparty politics to examine the formation of the United Kingdom coalition following the general election of 6 May 2010. It argues that the formation of the Conservative-Liberal Democrat coalition is not unusual in historical terms or in the context of contemporary European politics; and that although it is a break from the more recent pattern of postwar British politics it nevertheless does conform to expectations in the light of the coalition literature. The article also provides a comparative analysis of the impact of Britain's ‘First-Past-The-Post’ (FPTP) electoral system on party competition and an examination of the performance of the Alternative Vote (AV) system and argues that if the United Kingdom retains FPTP then a return to single-party government in 2015 is highly likely; and it is not inevitable that the introduction of AV would significantly advantage the Liberal Democrats.