North Korea’s cult of personality has been synonymous with the regime’s totalitarianism since the 1940s, bolstering the Kim family position and punishing dissenters.

It might seem curious then that a regime that so idolises its leaders refuses to publicly acknowledge Kim Jong-un’s birthday.

Monday 8 January is widely believed to be the Supreme Leader’s birthday, yet there is no mention of the date on the regime calendar.

The birthday of Mr Kim’s late father, Kim Jong-il, is celebrated every year on 16 February with a national holiday – the Day of the Shining Star. Equally, his grandfather Kim Il-sung’s birthday on 15 April is marked as the Day of the Sun. But no national holiday has been assigned to the youngest ruling leader.

Not only has his birthday never been publicly acknowledged, the regime has appeared in the past to go to great efforts to mask its existence.

In 2014, Dennis Rodman sang the soon-to-be 34-year-old “Happy Birthday” after an exhibition basketball match in Pyongyang. Viewers outside the so-called hermit kingdom were able to watch the video, but domestic audiences were simply told the former NBA player had “sung him a special song”.

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So why the secrecy?

Some believe the cloak and daggers may be a sign of respect for the elder Kims.

All North Koreans wear a pin over their left breast featuring the face of Kim Il-sung or Kim Jong-il – or both – as a sign of loyalty.

“There’s no doubt that he is the leader but it’s very early days yet in my view,” says Aidan Foster-Carter, honorary senior research fellow in sociology and modern Korea at Leeds University. “If he lives as long as his grandfather he could be around for another half century, so its part of this whole shtick of being the loyal follower. Likewise his picture is not on any badges, there are no statues of him, so I don’t find it anomalous.

“I think it would show unseemly haste if they were making him the focus for now.”

Dr Owen Miller, Korean studies lecturer at SOAS, agrees: “They might consider it too soon to take Kim Jong-un’s personality cult up to that level,” he says. “You have to consider that Kim Jong-il was anointed as successor in 1980 and his cult was built up long before he became leader. Kim Jong-un on the other hand was only introduced to North Koreans a year or two before he became leader in 2011.”

But the bizarre secrecy also speaks to the dark inner workings of the communist regime, where “everything operates on a need-to-know basis”, according to Foster-Carter. “If you’re in North Korea you only do your own job, you don’t look to the left or to the right,” he says. “I don’t think we know anything for sure about his popularity one way or another apart from it’s extremely dangerous to speak out against him.”

Birthday celebrations for the elder Kims currently involve mandatory viewings of state broadcasts praising the leaders. People mark the birthday of Kim Jong-suk – the deceased grandmother of Kim Jong-un, which falls on Christmas Eve, by making pilgrimages to a town in the north-east called Hoeryong - her birthplace.