'Canary in the coalmine' How Caerphilly's byelection could signal shift for UK politics

Usually, a Welsh parliament byelection in Caerphilly would not attract huge attention away from its rolling green hills and postindustrial townscapes.

- Steven Morris

But these are not normal times and the result of next month's ballot in this corner of south Wales may have ramifications across the UK.

Apologising for the cliche, Dr Jac Larner, a polling expert at Cardiff University who is from Caerphilly, said the byelection may be the "canary in the coalmine" for a fundamental change in UK politics.

Polling has suggested an ailing Labour party could be pushed into third place in one of its traditional heartlands by Reform UK and Plaid Cymru. If it proves to be correct, the shock waves will be felt not only in Cardiff but across the country.

"Labour is facing an existential crisis in Wales that threatens to end over a century of political dominance," Larner said. "Wales is the home of its first leader, Keir Hardie, and its spiritual leader, Aneurin Bevan, and by the next Senedd election [to take place in 2026] it will have been 103 years since Labour was not the largest party in a major Welsh election - the longest such streak of any party anywhere in the world."

The main route through the town of Caerphilly passes the biggest castle in Wales and a bronze statue of the magician and comedian Tommy Cooper. At the moment there are also three campaign offices on the main drag as Labour, Reform and Plaid all try to make their presence felt. When the Guardian visited, the contrast between the offices of the two leading contenders - Reform and Plaid - was marked.