Part of the crew of the film Crossing the Line.Provided to China Daily

In January, Cockerell became one of the first foreigners to hit the slopes of the Masik Pass Ski Resort. In 2012, Bonner whipped up a storm of controversy by producing the first foreign-made full-length feature film for the country. Short-film maker Anja Daelemans of Belgium co-directed. Cockerell also worked on the project.

The two Englishmen discussed making the film, Comrade Kim Goes Flying, and three documentaries shot in the country, as well as their experience of leading tours there, during a five-day publicity swing through Shanghai.

The movie, a romantic comedy, has been doing the rounds at international film festival for 18 months but has only been screened twice in China, including a showing in Shanghai in February.

It sounds on paper like a DPRK version of the 1983 Hollywood hit Flash Dance. But instead of an exotic dancer from Pittsburgh who welds steel by day while dreaming of becoming a ballerina, the plot revolves around a female miner who makes it as a national acrobat and falls in love along the way.

"I get into arguments with my girlfriend all the time about the legitimacy of projects like this and 'ethical tourism' when working with a country like North Korea," Bonner says.

"But at the end of the day we try to encourage as much interaction with tourists and local people as we can, which we think helps."

The US film authorities have blasted the pair for effectively supporting the country by producing a propaganda-laced movie, but other US critics and media including the Wall Street Journal have been more effusive in their praise.

Cockerell says: "Every film made in North Korea is a propaganda film. They all have to adhere to a playbook written by (late Dear Leader) Kim Jong-il two decades ago, which can create a lot of headaches."

In a country where many things appear off-kilter, both of the two leads were acrobats not actors, while one of the DPRK's top movie stars accepted a small supporting role.

The crew encountered numerous problems during pre-production and shooting. For example, actors are not allowed to kiss in DPRK movies. Love triangles are also banned.