Mr Speaker, it is to some people extraordinary that in Britain we still have a largely unwritten constitution.

BBC: In full: Constitution proposals

Deputy PM Nick Clegg argued that five years was "going with the grain of some of the founding texts of our unwritten constitution" - referring specifically to legislation which set the maximum limit at five years.

BBC: Q&A: Fixed term parliaments

The unwritten British constitution in this situation allows for the incumbent party, in this case, the Labour Party, led by Prime Minister Gordon Brown to seek a coalition deal.

FORBES: Britain: Hung, Drawn And Quartered

The clarity of a written constitution may give America an advantage over many European countries, where unwritten custom has more sway.

ECONOMIST: Islam and demography