Opinion polls suggest that the Labour Party in Scotland will struggle to win back the Catholic voters it was once able to count on, but who in recent years have switched their allegiance to the SNP. Scotland’s leading historian explains the causes of this ‘great political earthquake’ / By Tom Devine

The overwhelming majority of  Scottish Catholics in 2017 are descendants of the great stream of migrants from Ireland who settled in the industrial heartlands of Scotland in the nineteenth and early-twentieth centuries.

In the Victorian era, measured per head of population, there were more Irish in Scotland than in England and Wales: more than 7 per cent of the population compared with 3 per cent. Most of them were Catholic, but around a quarter were Protestants from the counties of Antrim and Down.

Scottish Catholics took part enthusiastically in the campaign for Irish Home Rule from 1870 and, after the Easter Rising of 1916, Sinn Féin became a popular force in the Irish communities. But the bloodletting of the civil war that followed the foundation of the Irish Free State in 1922 caused widespread disenchantment, and effectively brought the Scottish-Irish political connection, which had endured for more than half a century, to an end.