Political leaders have begun a last-ditch bid for votes ahead of Thursday’s elections, as campaigning enters its final day.
Prime Minister Boris Johnson will make a last pitch for votes in England, where thousands of council seats are up for grabs.
Meanwhile, Sir Keir Starmer will join Labour candidates in three races for local mayors.
Polls will open at 07.00 BST on Thursday, with results due from Friday.
About 48 million people in England, Wales and Scotland will be able to take part in a series of elections taking place against the backdrop of Covid-19.
As well as polls for the Scottish Parliament and the Senedd in Wales, there are elections for seats on 143 English councils and 13 local mayors.
Thursday’s votes represent the first electoral test for parties since December 2019, when the Conservatives won a majority at the general election.
They will be the first votes since Sir Keir took over as Labour leader 13 months ago and Sir Ed Davey won the Liberal Democrat leadership race last August.
As well as elections postponed last year due to Covid, Thursday’s bumper crop of votes will also see a by-election for the Westminster seat of Hartlepool.
Campaigning has been curtailed by Covid restrictions, with large public meetings moved online and limits on groups of activists going door-to-door.
Sir Keir will begin a frantic day of campaigning on Wednesday with a visit to Pontefract to support the party’s candidate for West Yorkshire mayor.
Later, he will join Labour’s candidates for the mayoral races in the West Midlands and West of England.
Sir Ed Davey will take the Lib Dems’ campaign to the London suburb of Surbiton, where he is expected to highlight the party’s policies on the environment.
Meanwhile, Green Party co-leader Jonathan Bartley will also be in the capital to support the party’s candidate for the Greater London mayor.
The pandemic means ballots are expected to take longer than usual to count, which means greater uncertainty over when results will be declared.
Some counts will take place overnight on Thursday, including for the Hartlepool by-election, where a result is expected by Friday morning.
But counting in some council areas in England will take place on Friday, or over the weekend.
A dozen of the counts for 39 police and crime commissioners elected in England won’t begin until Monday.
Results for all 60 seats in the Welsh Senedd will be known on Friday.
Scotland starts counting in some areas on Friday, but there won’t be a final result until Saturday, or possibly even Sunday.