‘Seismic change’: how election wins for nationalists in Celtic nations could reshape UK

With polls suggesting Plaid Cymru, the SNP and Sinn Fein could be in power after May vote, constitutional challenges may lie ahead

In four weeks, the shape of British politics is likely to change dramatically. For the first time, nationalists who aspire to break up the UK are expected to be in control of Scotland, Wales and Northern Ireland simultaneously. The change will be seismic," said Angus Robertson, a senior minister in the Scottish government.

Opinion polls consistently suggest that after the elections on 7 May, England will be flanked by countries run by restless centre-left nationalist parties - Plaid Cymru in Cardiff, the Scottish National party in Edinburgh and, in Belfast, Sinn Fein, which shares power with the Democratic Unionists.