Polling has opened across England, Scotland and Wales in a series of local, mayoral and parliamentary contests – the biggest electoral test Keir Starmer and the Labour government have faced since the 2024 general election.

As millions of people across Great Britain go to the polls on Thursday, party leaders are poised for a set of results that could fundamentally change the political landscape nationally in Scotland and Wales, and across local authorities in England.

The results will be closely watched by all parties, and are seen as the first major political test of an increasingly multiparty system.…