For years, Woo Seung-yep was a lone voice in the wilderness, warning fellow South Koreans to prepare for impending doom. But as tensions with North Korea rapidly escalate, he is no longer mocked.

Mr Woo, 44, has become the face of the South’s war preppers, a growing band of urban-disaster specialists who keep survival bags laden with essentials that they can grab at a moment’s notice to one of the country’s many nuclear fallout shelters.

In recent months he has seen a surge in interest in his online forum, Survival 21, founded in 2010 to discuss how to stay alive during war, disaster or nuclear holocaust.

Close to 20,000, among them teenagers, old people, business executives, professors and students, have now signed up.

“Many members profess their worries,” the former office worker told The Telegraph in an interview. “The main question today is ‘will a war break out in Korea? And if so, when would that be?’”

Mr Woo, who has advised on a government awareness manual, tells his followers to keep a survival pack stocked at all times and to know where to run to if conflict breaks out.

His own emergency supplies include water, freeze-dried food, a torch, radio, hat, raincoat, medical kit and warm blanket.