The fortunes of the port town of Barrow-in-Furness have long been tied to the British defense industry. Generations of its families have spent their entire working life at "the yard,” where the U.K.’s nuclear submarines are built.

Today, two-thirds of the town’s working population is employed by BAE Systems PLC, which operates the shipyard, its vast Devonshire Dock Hall dominating the local skyline.

When it comes to elections, "Barrow is one of the the very few seats in the country that can be decisively swayed by a single national issue,” said John Woodcock, who was Labour MP for Barrow-in-Furness until 2015. "It’s always jobs in the shipyard.”