"I don't think [Nick Clegg] knows what will hit him. The constitution is like the Bermuda triangle" - Lord Hennessy
After Lib Dem leader Nick Clegg agreed to take his party into coalition with the Conservatives, he pledged to bring in "the biggest shake-up of our democracy since 1832".
In government, he became the deputy prime minister with special responsibility for political and constitutional reform. So how are his plans progressing?
Mr Clegg says the current system, where the timing of elections is largely left to the whim of the sitting prime minister, can leave governments "distorted, paralysed, hobbled and handicapped". Legislation paving the way for fixed terms of five years has cleared the Commons but now faces a torrid passage through the Lords, with peers arguing emphatically that four years would be more appropriate.
At Mr Clegg's instigation, voters went to the polls on 5 May 2011, in only the second nationwide referendum in the UK's history, to decide on whether to stick with first past the post, the current system used to elect MPs, or switch to the alternative vote (AV), a system where candidates may be ranked in order of preference.
The move was overwhelmingly rejected.
The bill that allows for the referendum - the Parliamentary Voting System and Constituencies Bill - also dramatically changes the size and number of UK parliamentary constituencies. As a result of these changes, there will be 600 MPs - 50 fewer than now - representing a number of constituents that will not be allowed to vary by more than 5% around an average of about 76,000.
In 2010, some constituencies deviated by more than 25% from the average. Four constituencies, all based on islands where enforcing this rule would be particularly impractical, will be exempt from the boundary review.
The coalition is committed to changing the make up of the Lords, from a wholly appointed chamber to a fully, or partly, elected chamber. Detailed plans have not yet been published.
Power of recall
In future, constituents will be able to recall MPs guilty of "serious wrongdoing", paving the way for a by-election. Full details of this plan, including the specific types of wrongdoing meant, are yet to be confirmed.
Targeting seats that have had the same MP for many years, the coalition document suggested voters should be able to choose the candidates standing at future general elections - rather than having their candidates foisted upon them by political parties. But this plan has since been ditched to save money.
MPs have approved legislation aiming to reaffirm parliamentary sovereignty over EU institutions and committing the government to hold a referendum on future EU treaty changes judged by ministers to represent "significant" transfers of power from Westminster to the EU. The bill now faces scrutiny in the Lords.
The government is pushing ahead with many of the recommendations of the Calman commission, handing more power over income tax to the Scottish Parliament and enabling Holyrood to borrow funds for the first time for capital investment projects.
Welsh Secretary Cheryl Gillan recently announced that the government plans to establish a Calman-like commission to assess the devolution settlement in Wales.