What are jacket potatoes, and why are the English waiting hours for them?

IT’S lunchtime on a bright and blustery fall day in Preston, in the northwest of England. Across the Flag Market, a vast, tree-lined plaza in the shadow of a colonnaded, Victorian museum, an ever-growing line of roughly 150 people waits patiently for their turn at a modest cherry-red trailer. This is the daily wait – anywhere between two and six hours. Party music booms out from within the trailer’s steaming, open hatch, and selfie-seeking customers approach the counter with raised smartphone cameras and big, expectant grins. You’d be forgiven for assuming that the foodstuff prompting this fervent excitement might be…