Jong-un 'losing grip on power as chiefs defect'
Within seconds of arriving at the North Korean border, a US army soldier leapt on to the tour bus and started barking orders.
"No drugs," he said, glowering at the group of mainly US tourists. "No alcohol. No weapons of any kind, not even penknives. And do not, under any circumstances, attempt to communicate with the North Korean soldiers you are about to see."
He marched up and down, checking passports, before spinning around again.
"Another thing," he added, "and this is not a joke - are any of you considering defecting to North Korea?"
After answering, "No", the group was marched in single file into the Demilitiarised Zone (DMZ), a twisting snake of barbed-wire fences, watchtowers and minefields that bisects the Korean peninsula.
Tensions here have been near boiling point since the North Korean dictator Kim Jong-un threatened "imminent" war against the US.
Last Friday, Jong-un tested another intercontinental ballistic missile, which exploded just after take-off. US President Donald Trump, who has repeatedly threatened Jong-un with a "major" military response unless he ceases nuclear weapons tests, said the move "disrespected the wishes of China", North Korea's only ally.
Perhaps surprisingly, the US president's tough stance seems to have gone down well with many South Koreans.
"When Trump was elected everyone thought he was crazy, but now some think maybe he is the right person to improve things," said one DMZ tour guide.
There were few signs of complacency in the DMZ. The bleak, mountainous landscape is dotted at 100-metre intervals with guard towers manned by stern-looking soldiers who keep their rifles trained on the North. At the heart of the zone lies the "truce village" of Panmunjom, a cluster of blue huts where the North has been invited to take part in peace negotiations with the UN.
Though large swathes of this joint security area are on lockdown due to the tensions, visitors yesterday were allowed to briefly enter North Korean territory inside one of the huts, which straddles the official border known as the military demarcation line.
Stepping through the door at the end of the hut towards the North Korean countryside is strictly forbidden, with two taekwondo-trained soldiers stationed outside to deter any would-be defectors.
But a small window at the rear offered a view of a grim military building where a sullen North Korean soldier in a brown uniform stood guard.
"That guy's gonna be standing there for the next 12 hours at least," observed one US army escort. "That's North Korea for you." Though North Korean propaganda presents Jong-un as having absolute control, regime insiders have said his grip on power is slipping.
"We are seeing more and more members of the Pyongyang elite such as military commanders defect to the South," said Kang Cheol-hwan, head of the defector-led North Korean Strategy Centre.
"They are telling us that some have become tired of his recklessness and unpredictability. They say some generals might decide to remove Kim Jong-un with a military coup," added Cheol-hwan, who spent 10 years as a political prisoner in a North Korean labour camp before fleeing across the Chinese border in 1992.
That some North Korean chiefs would consider a rebellion used to be unthinkable, partly because of Jong-un's brutal purges of disloyal cabinet members. In 2013, Jong-un (33) infamously had his own uncle Jang Song-thaek executed with an anti-aircraft gun.
Back at the DMZ, the tour guide - who has followed North-South relations for 50 years - said he feared he would not see the peninsula reunited in his lifetime.
"It would be harder than it was to reunite east and west Germany," he said. "Even if it happened, the collapse of the regime, and the financial burden it would put on the South, would cause chaos. It is sad because though we are split in two we have the same culture, the same language, even the same alphabet.
"But if I lived for another 200 years, I still don't think I'd see us brought back together."