The U.K. has a general election tomorrow. The British system of government has always confused me – you mean it’s not written down?* you mean the Prime Minister can call an election whenever he wants? – so I decided to do a little research. Someone posted a nice overview of the British system as a comment on Matt P.’s blog.

I also found this on Wikipedia:

The term of a Prime Minister is linked to the term of Members of the House of Commons. Parliament has a maximum term of five years [ever since the Parliament Act of 1911]; in practice, however, it is usually “dissolved” sooner by the Sovereign, acting on a request from the Prime Minister. The Prime Minister normally chooses the moment most advantageous to his or her party for the dissolution. In some circumstances, however, the Prime Minister may be compelled to dissolve Parliament (or, if he or she prefers, to resign) by the House of Commons. The House may attempt to force the dissolution by passing a Motion of No Confidence or by rejecting a Motion of Confidence. The same effect is achieved if the House of Commons rejects the Budget (“withdraws Supply”), or if it rejects some other important component of the Government’s agenda. Such defeats for the Government, however, are rare; there have only been three defeats on confidence issues since the nineteenth century: twice in 1924, and once in 1979. …

Whatever the reason… the dissolution is followed by general elections. If his or her party has lost a majority in the House of Commons, the Prime Minister is compelled to resign (or request a dissolution, but the Sovereign is not compelled to accept such a request). The leader of the party or coalition now in the majority is then appointed Prime Minister by the Sovereign. …

Much more fascinating stuff about the British political and constitutional system here, here and here.

* Turns out some of it is written down.