Elections took place for the Scottish parliament, Welsh assembly and 344 councils in England and Scotland.There are also contests for elected mayors in Bedford, Mansfield and Middlesbrough.
Voters in the Scottish parliament and Welsh assembly elections used a two-stage proportional representation system. This keeps traditional first-past-the-post constituencies, but also provides for further seats to be filled to "top up" parties who fare disproportionately badly in the winner-takes-all contests.
Electors will have two ballot choices. The first will be to directly elect a member in a local constituency - 73 in Scotland and 40 in Wales. The second will be cast for parties - not candidates - in "top-up" regional constituencies. Scots will choose 56 members in eight constituencies for an overall total of 129. In Wales, 20 will be elected in five regional constituencies, making a grand total of 60 seats in the Assembly.
Parties will be required to submit lists of those they wish to be returned in the regional constituencies. They will also put them in their preferred order. If a party is entitled to a seat the candidate who is top of its list will be declared elected. In Scotland, if that person has already been elected in a FPP constituency, the top-up seat will go to the next on the list. In Wales, candidates are not allowed to stand for both a first-past-the-post constituency and a PR one.
In the Scottish local elections voters will use the single transferable vote system as used in Ireland.