Coalition negotiations between the Liberal Democrats and the Conservatives produced agreement regarding some fundamental changes to the British electoral system.
One of those changes is that Parliament should sit for a fixed term of five years, before the next general election. That will end the traditional practice, which I described here and here, of allowing the prime minister to set the election date.
The other method of cutting short the term of a Parliament has been the vote of no confidence. By a simple-majority vote, the House of Commons has been able to, in effect, fire the prime minister. Under the coalition agreement, that will still be allowed, but it will require a supermajority of 55%.
A no-confidence motion could be blocked by 294 MPs. The Conservatives, with 306 seats (and possibly 307 after the delayed vote in one constituency), could defeat such a motion, unless (as if often the case for a governing party) their numbers are eroded over the next five years via by-election losses.
In the short term, the effect will be to lock the two coalition parties into their deal, and not enable either of them to bring about the scenario that many had expected, i.e., another general election within a year or so, to try to resolve the deadlock, and produce a parliamentary majority for one party or another.
In the long run, it will probably change British politics in ways that are neither intended nor anticipated.
Also, the two parties are committed to a referendum on adopting the Alternative Vote system for electing the House of Commons. That method is sometimes called Instant Runoff Voting, and I described it here, in an American context.
While falling short of the Liberal Democrats' ultimate goal of proportional representation, Alternative Vote might increase support for that party in future elections, and make coalition negotiations, such as those that have taken place over the last few days, commonplace in Britain.