North Korea does not have the greatest reputation abroad - death camps, dictators and nuclear-missile-testing don't make for good PR. But in some Asian cities the Pyongyang restaurant chain is seeking to change minds with good food and great service.

I've travelled the world quite a bit but I can honestly say I've never encountered restaurant staff quite as talented as this.

After depositing their plates of food, waitress after waitress stepped up on to the stage to deliver a series of virtuoso numbers - Yong with her operatic arias, Ji-u on the violin, or Lin-a with her remarkable whirling dervish routine, balancing a pot on her head.

All of these performances were served up to a thumping electronic beat, while rose-tinted images of the Dear Homeland flashed up on a screen behind them.

I have to admit I became quite transported by it all. But perhaps this was the beer, and the enthusiastic crowd, who clapped and cheered throughout.

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We'd been served tasty if overpriced Korean dishes - dog-meat casserole and pine-nut gruel among them. And there was a range of exotic $50 beverages, flavoured with ginseng and sea cucumber, plus herbal pills which, the waitress told me, really could cure anything.

But the question is - and I suppose the reason many foreigners like me wander into this place - what exactly are we coming to be cured of?

The nights I went in the place was packed, overwhelmingly with South Korean or Chinese expats, mostly large gangs of them drunkenly flirting with the staff.

The servers would dance elegantly between the tables in their colourful peasant smocks, smiling as they side-stepped the occasional groping hand of a client.

It led me to ponder one circulating theory - that this was all a complex form of espionage... the talented and attractive waitresses had been placed here to seduce high-value visitors, like me perhaps, to extract valuable state secrets?

To test that idea, I ventured a conversation with Yong, the waitress serving me, who did speak some English.

"How are you? Where are you from?"

"Pyongyang", she replied (OK, so that was a pretty stupid question).

"How long are you here in Cambodia?"

"Three years. I go home in one year."

"You like it here? You want to stay here?"

"No, I miss Pyongyang," she replied.

Image copyright AFP

I wasn't sure but did I detect a slight clenching of her jaw there?

She was polite but a little stiff. If this was seduction, I was Kim Il Sung. I tried a more direct approach.

"Where do you live?"

Media playback is unsupported on your device Media caption Listen to the waitresses singing in Ed Butler's report for Business Daily

"Upstairs."

"Gosh, how many of you live up there?"

"A secret. It's a secret," she smiled icily. And then, more firmly, as I moved to pull out my camera, "No, no photos allowed."

So instead I turned to an elderly South Korean doctor sitting nearby. He told me he'd recently been asked to treat a couple of the young ladies when they'd got sick.

They were not normally allowed out, he said.

"They were all highly trained at the State Arts College," he told me. "They were the most talented girls."

But here they find themselves watched night and day. The waitresses watch each other, the chef is watching the waitresses, someone is even watching the chef.

Image copyright AFP Image caption A Pyongyang restaurant opened in Amsterdam in 2012 - and closed later that year

Image copyright AFP Image caption Some of the restaurants of the Pyongyang chain are in China, including this one in Dandong

I decided to do some internet searching on my phone. Reports of defections from these places are actually pretty few and far between.

The staff, of course, have families back home, and experts say it could go very hard on them if anyone tried to run away - although one or two restaurant managers have been known to abscond with bags of cash.

On those occasions, restaurants had been shut down entirely.

The working assumption, according to most reports, is that the Pyongyang chain is primarily there to make money, to feed the North Korean leadership's desperate need for foreign currency.

Some speculate that the restaurants are in fact directly under the wing of the secretive Bureau 39, an agency that allegedly launders cash for the government through ventures that include arms sales and methamphetamine production.

But to be fair, there was absolutely no sign of that here. And anyway, given all the staff, pleasant decor and equipment, it occurred to me that this little place was hardly going to provide that much of a boost to the nation's struggling balance sheet.

I turned back to the Korean doctor. What did he think? Could these women be spies, or was this just a money-laundering operation?

He shrugged doubtfully. Maybe it wasn't about money or politics at all. Maybe the North Koreans just want to put on a show - to smile and to sing - they just want to be loved.

Maybe.

I am pleased to disclose that, after some persuasion, one waitress, Lin-a, did relent - she posed for a photo with me. In the picture she can be seen smiling in her peasant frock. I'm smiling, too, in my jeans.

And behind us, next to an epic mural of a rising Korean sun, stands another waitress, watching us.

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