In what has so far been a significant and tumultuous year of political events, the Prime Minister has ensured yet more drama by announcing her intention to seek a UK general election on Thursday 8 June 2017.

It used to be that Prime Ministers simply required to go to Buckingham Palace to ask the Queen to dissolve Parliament and call a new election, as the dissolution of Parliament was part of the (now famous, following the 'Article 50 case' earlier this year) Royal Prerogative.However, the UK constitution has been revised in recent years.

Thanks to the Fixed Term Parliaments Act 2011, the calling of a general election is now a statutory rather than a prerogative matter. The standard rule now is that the UK Parliament sits for fixed terms of five years between general elections. The next general election was due to fall in the first Thursday in May 2020. However, the 2011 Act allows two routes by which an early general election can be held.

Three routes to a general election

The first is for the House of Commons to pass a vote of no confidence in the Government, with a general election following (unless the Commons changes its mind within 14 days).

The second route, and the one the Prime Minister is pursuing, is for two thirds of MPs to vote in favour of a motion for an early election.

This requires MPs representing two thirds of all constituencies (i.e. including vacant seats and MPs who have never taken their seats such as those of Sinn Fein, not just two thirds of those MPs voting) to agree to the motion.

A third route to an election could be the repeal of the 2011 Act, which would require only a simple majority of MPs (see this piece in The Scotsman by Christine, on an early version of the proposals that led to the 2011 Act).

In such a scenario Parliament may have to put in place new arrangements for calling elections, on the basis that the old prerogative power may not simply revive as a result of the repeal. It appears such a drastic step will not be required, however, as enough opposition MPs look likely to vote in favour of the motion to meet the two-thirds threshold. The motion for an early election, which the Prime Minister announced will be put to the House of Commons tomorrow, can therefore be expected to pass.

That will of course have a number of hugely significant consequences, but one technical point worth noting is that the Scottish Parliament last year set its next election for 6 May 2021, making the current term five years rather than the usual four (as prescribed by section 2 of the Scotland Act 1998). It did that because the standard four-year timetable would have seen the next Holyrood election held on the same day as the scheduled UK general election in 2020.

Last year's Scottish Parliament election had itself been postponed by a year in order to avoid clashing with the 2015 UK election, causing this year's local government elections (which would have been scheduled for 2016) to follow suit.

This desire to avoid clashes followed the 2007 Scottish Parliament and local authority elections, which took place on the same day and saw apparent confusion over the different electoral systems. To avoid a repeat, the subsequent local elections were pushed back from 2011 to 2012.

Five year terms

Five year terms had therefore become the new normal, if only unofficially, given that the Scottish Parliament could not revert to a standard four-year term without clashing with a scheduled UK election. Every postponement in a Holyrood election then had a knock-on effect on the local government election schedule.

However, an early UK election will break that cycle.

Holyrood could therefore reinstate four-year terms immediately, by legislating to revert to 2020 and 2021 (respectively) for the next Scottish Parliament and local elections.If it does so, and assuming Westminster retains a five-year term, no further clashes would arise until 2032.

If the Scottish Parliament does not act, its own four-year cycle will resume automatically after 2021 and no clashes with Westminster will arise until 2037. However, something would have to be done about the next UK and local government elections both being scheduled for 2022.

Accordingly, and albeit it was surely not a consideration (or at least not a prominent one), the Prime Minister's announcement today could result in the current Scottish Government's term being one year shorter than expected.