Britain is back on Arctic-assault alert amid warnings to brace for the return of the ‘Troll from Trondheim’. Mild, spring-like temperatures are about to give way to an imminent -10C Scandinavian snow blast. A ‘major change’ back to winter has prompted government forecasters to issue a week-long raft of severe weather alerts. Temperatures will nosedive through the coming days before the weekend brings the risk of widespread snow. Bitter winds will sweep in from Scandinavia raising the chilly spectre of last winter’s ‘Troll from Trondheim’. Jim Dale, meteorologist for British Weather Services, s…