At Kuala Lumpur International Airport on Monday morning, the dark-haired, demure young woman in the short blue skirt and pink tights attracted little attention.

Strolling casually through Terminal 2, a small bag on her shoulder and the initials LOL (text-speak for ‘Laugh out Loud’) on her white T-shirt, she was just one of the 150,000 or so passengers the Malaysian hub handles each day.

But there was nothing casual about this woman. She was a trained assassin on a mission to kill, and somewhere in the milling crowds was her female accomplice.

They were stalking their target, a short, overweight playboy with a taste for women, whisky, gambling — and insulting his half-brother, Kim Jong-un, the despotic Supreme Leader of the barbaric regime in North Korea.

How the chillingly audacious murder of North Korean tyrant's brother in a major airport may have involved a poisonous handkerchief and fountain pen

It was a regime that the ‘target’ repeatedly dismissed as — to use his own words — ‘a joke to the outside world’.

His name was Kim Jong-nam, and at 45 he was a man who had lived with the threat of death for years, since fleeing North Korea in fear of torture and execution. There had already been one botched attempt on his life.

He travelled with bodyguards on his regular trips in Asia and occasionally Europe, usually on a false passport, in this case under the name of Kim Chol. But a brief lapse in his personal security between arriving at the airport and proceeding to passport control for his flight to Macau, where he lives in exile, left Kim Jong-nam alone. It was this that allowed the assassins to strike in the shopping concourse.

One of the women is believed to have grabbed his face from behind — possibly placing a poison-laced handkerchief on his mouth — while the other sprayed toxic liquid on him or injected him with poison.

The dark-haired, demure young woman in the short blue skirt and pink tights attracted little attention in Kuala Lumpur at first

According to U.S. sources, a ‘fountain pen’ may have been used — a device previously associated with North Korean assassinations.

An agent arrested on a mission last year revealed how he was equipped by North Korean Intelligence with what looked like a Parker pen, but contained a retractable needle for administering a fatal dose of a toxin described as ‘more potent than cyanide’.

It caused muscle paralysis, breathlessness, suffocation and death, and was the method of choice for covert killings.

Whatever Kim Jong-nam was exposed to, the effect was immediate. As the women fled into a cab, he stumbled and gasped for breath, begging for help.

He complained of burning eyes and a severe headache before suffering a seizure and dying in the ambulance en route to hospital.

Yesterday, the alleged North Korean female agent was arrested over the death. According to Malaysian police chief Khalid Abu Bakar, she had been ‘positively identified’ from CCTV footage of her wearing a denim skirt and the distinctive T-shirt as she escaped the scene.

She was travelling on a Vietnamese passport in the name of 28-year-old Doan Thi Huong. This is believed by police to be a false identity.

After her arrest, she is said to have told investigators she was asked to hold a handkerchief on the face of the victim after he had been sprayed by the other woman as part of a ‘prank’, it was claimed in one report.

Investigators were last night hunting her female accomplice and four men also believed to be involved in what is being described as a classic Cold War-style hit.

She was then seen hailing a cab outside the airport on CCTV but the Malaysian authorities claim to have since arrested the suspect, who was carrying a Vietnamese passport

Cheong Seong-Chang, of the independent Sejong Institute in Seoul, South Korea, said the assassination was ‘unthinkable without a direct order or approval from Kim Jong-un himself’.

Jong-nam’s killing was probably motivated by a recent news report that he had sought to defect to the EU, the U.S. or South Korea as far back as 2012.

Just days after the international condemnation of North Korea’s ‘game-changing’ latest ballistic missile test, the assassination on foreign soil has prompted further outrage.

Adding insult to injury, North Korean officials are attempting to block the autopsy on Jong-nam as they demand to take the body back to Pyongyang.

Jong-nam, who openly criticised the North Korean regime as 'a joke to the outside world', has sought to defect since 2012

For 33-year-old Kim Jong-un, the burial of his half-brother will bring to a triumphant end to a long-running saga of jealousy, paranoia and, ultimately, fratricide that would not have seemed out of place in Ancient Rome.

Kim Jong-nam was once the heir apparent of North Korea, the eldest, albeit illegitimate, son of the ‘Dear Leader’, Kim Jong-il, by a South Korean actress (who died in mysterious circumstances in Moscow in 2002).

His existence was kept secret by his father for many years, and he was not allowed to mix with his siblings from Kim Jong-il’s other affairs and marriages.

However, he wanted for nothing, living in a mansion, surrounded by the latest toys from Europe and being driven on jaunts around the North Korean capital in a black Mercedes. At the age of ten he was sent abroad to study at the International School of Berne in Switzerland, where he became fluent in French.

On his return to North Korea aged 17, Kim Jong-nam enrolled at a university. But his relationship with his father had deteriorated and he blamed his younger half-brother, Kim Jong-un, for taking advantage of his father’s loneliness while he was out of the country.

But Kim Jong-nam was a young man whose European experiences had filled him full of ‘dangerous ideas’, such as free market reforms to end rampant poverty and starvation in his home country.

These suggestions outraged his father and caused apoplexy among the ruling elite. ‘I was viewed with suspicion,’ he admitted.

At the age of ten he was sent abroad to study at the International School of Berne in Switzerland, where he became fluent in French

His spell in Switzerland had also introduced him to life’s luxuries — and to sex. Despite Japan being a sworn enemy of the regime, he would regularly fly to Tokyo using a false passport to indulge his playboy lifestyle in nightclubs, casinos and the city’s red-light district. The tubby Korean, just 5ft 2in tall and weighing 14st, was a regular at an establishment known as Soap Land, where hostesses charge clients up to £300 an hour for their services.

In 2001 he was caught in Tokyo on a false passport, on a trip to Japan’s Disneyland. Retribution was swift and he was imprisoned for three days by his father before being banished from North Korea for ever. He lived in Singapore, Indonesia, Malaysia and France, acquiring two wives and a son, before settling in the Chinese territor of Macau, where his lavish lifestyle was bankrolled by China — a huge power behind the scenes in North Korea.

Beijing saw the exiled brother as a useful asset should they ever need to attempt to replace the ‘Supreme Leader’ with another member of the dynasty.

When Kim Jong-un came to power in 2011 after the Dear Leader’s death, his half-brother never lost an opportunity to attack his regime, claiming that without reforms North Korea would collapse and decrying the herditary transition of power. Recklessly, he encouraged speculation that he could one day replace his half-brother.

Inevitably, North Korea’s intelligence agency, the Reconnaissance General Bureau, saw him as a threat and monitored him closely. In 2011 there was an attempt on his life in Macau, resulting in a bloody shootout with his bodyguards.

When Kim Jong-un (pictured in 2010) came to power in 2011 after the Dear Leader’s death, his half-brother never lost an opportunity to attack his regime

Indeed, it emerged last night that Kim Jong-nam had written to his half-brother as long ago as 2012, begging him to spare his life and his family.

‘I hope you can cancel the order for the punishment of me and my family,’ the letter stated. ‘We have nowhere to go, nowhere to hide, and we know that the only way to escape is committing suicide.’

North Korea has so far made no comment about a murder that is making headlines around the world. Significantly, the death of a close relative of the ruling family in such strange circumstances has not merited a single word in the state-controlled media.

Such censorship is the norm in North Korea, a country of 24 million where the majority go without food and the country’s ruling elite lead lives of extreme privilege, with lobsters and Kobe beef flown in from abroad for official dinners.

By contrast, chronically malnourished North Koreans have literally shrunk over the years. With millions starving, they are now, on average, 5in shorter than those just across the border in the South.

Citizens are under 24-hour surveillance. Televisions can only receive government stations; mobile phones are the preserve of a tiny elite, and the internet is banned. All public telephones are monitored and nobody is allowed to leave. Ever.

Jong-nam was killed at Kuala Lumpur International Airport (pictured, file image), in an audacious attack thought to have been carried out by two women

Kim Jong-un has retained the system introduced by his father, the Dear Leader, a chronic alcoholic who accumulated a fortune of around £4 billion, that has seen hundreds of thousands of his subjects jailed. Three generations of a family will be punished if just one person speaks ill of him.

Executions and torture are rife. According to rare accounts from defectors, specially trained dogs are set on prisoners to maul them to death. Others are beaten and shot through the head. There have been horrifying accounts of foetuses cut from the wombs of female prisoners.

Kim Jong-un has ordered horrific punishment of opponents and reportedly had 11 former girlfriends executed before his marriage. His defence minister was publicly executed with an anti-aircraft gun for answering back and falling asleep during military meetings, and his uncle Kim was shot after committing ‘tremendous crimes against the government’.

The Supreme Leader himself, married with a young child, lives in seclusion in a mountainous area that can only be reached by an underground road. Here, alongside his command centre, fighter jets and helicopters are on constant stand-by inside bunkers dug deep into the mountain.

This subterranean lair also boasts a 50-metre swimming pool, which features a massive portrait of Jong-un, made from gold tiles, on the bottom.

Blacklisted by the U.S. and targeted with sanctions, Kim Jong-un is viewed by Western intelligence officials as a danger to the whole world.

As police carried out forensic tests last night, Malaysian authorities declined to return Kim Jong-nam’s body to Pyongyang, perhaps denying his sadistic half-brother the final victory.