It has been pointed out before that the SNP and the Scottish Conservatives have something of a symbiotic relationship. Bitterly opposed as they are on the constitutional question, they nonetheless share an electoral interest in keeping that question front and centre.

This explains the otherwise baffling (to put it politely) decision by the Tories to put the Nationalists’ central election message – that an SNP majority means another referendum – at the top of their own election materials.