Great British voters will head to the polls today (May 6) on what has been dubbed “Super Thursday”.

Polling station have opened for voters to cast their ballots in elections which could shake up British politics and have profound implications for the future of the United Kingdom.

The future of the Labour party and thoughts on the union are key issues at play in what will be the biggest indicator of public opinion outside of a general election

So what elections are taking place and what are the systems being used?

– Scottish Parliament

Scottish Parliament, EdinburghThe Scottish Parliament building at Holyrood in Edinburgh (Jane Barlow/PA)

Voters in Scotland will elect 129 MSPs in a crucial contest which will give an indication of the level of support for the SNP’s push for a fresh vote on independence.

People will cast two ballots under the additional member system – a form of proportional representation – electing both constituency and regional MSPs.

Votes for the individual candidates in the 73 constituencies are counted first.

The 56 regional MSPs – split across eight regions – are elected using a formula aimed at ensuring that the number of seats a party gets in total across a region is about the same as the percentage of votes it receives.

– Welsh Parliament

Royal visit to CardiffThe Senedd in Cardiff Bay (Steve Parsons/PA)

Labour has run Wales since devolution and Mark Drakeford hopes to maintain the party’s grip on the Senedd.

The additional member system is used to elect 40 constituency and 20 regional members.

– Hartlepool by-election

The contest to elect Hartlepool’s next MP provides a key test for Labour leader Sir Keir Starmer. The party held the seat in 2019 with a majority of 3,595.

But the “red wall” across the north crumbled, handing Boris Johnson the keys to No 10, so the by-election will give an indication of whether Sir Keir has been able to reverse the process that has seen Labour’s heartlands disappear.

Hartlepool by-electionLabour Party leader Sir Keir Starmer meets local people in Seaton Carew in County Durham during a day of campaigning for the Hartlepool by-election with the party’s candidate, Dr Paul Williams (Stefan Rousseau/PA)

Bookmakers have made the Tories odd-on favourites to secure the seat, a rare feat for a governing party.

As in a general election, the first-past-the-post system is used – whoever gets the most votes wins the seat.

– London

In London, Labour’s Sadiq Khan is the bookies’ favourite to retain City Hall.

London Mayoral electionSadiq Khan hopes for a second term as London’s mayor (Stefan Rousseau/PA)

Voters choose the mayor using the supplementary vote system, picking a first and a second preference for the job. If a candidate receives more than half of all the first choice votes they are elected. If this does not happen, the two candidates with the most first choice votes go through to another round, with second preferences from the eliminated candidates taken into account.

Voters in the capital will also elect 25 London Assembly Members using a system similar to that in Scotland and Wales.

– English mayors

Regional mayors will be elected for Cambridgeshire & Peterborough, Greater Manchester, the Liverpool City Region, Tees Valley, West Midlands, West of England and – for the first time – West Yorkshire. High-profile names seeking re-election include Labour’s Andy Burnham in Greater Manchester and Tory Andy Street in the West Midlands.

Local electionsPrime Minister Boris Johnson sips a pint in the beer garden with West Midlands Mayor Andy Street during a campaign visit (Jacob King/PA)

Five local mayors are also due to be elected on May 6, for the local authorities of Bristol, Doncaster, Liverpool, North Tyneside and Salford.

Like the London mayoral contest, the supplementary vote system is used.

– Local elections

There will be 21 county councils holding elections, along with 28 unitary authorities, 59 district councils and 35 of the 36 metropolitan boroughs (the one exception is Birmingham, where elections will take place in 2022). All use the first-past-the-post system.

– Police and Crime Commissioner (PCC) elections

PCCs will be elected in all areas of England apart from London, Greater Manchester and West Yorkshire, where these powers are held by the directly-elected mayor. A total of 39 commissioners will be chosen across England and Wales using the supplementary vote system.