The wild, indulgent lifestyle of the Happy Valley set was governed by the three As: "altitude, alcohol, and adultery".
But for the group of foreign aristocrats who moved to the Kenyan highlands to escape the drudgery of World War II, it was never supposed to end in murder.
On the morning of January 24, 1941, the body of a dashing British earl was found slumped over the wheel of his car on a lonely road on the outskirts of Nairobi.
He'd been swiftly dispatched with a bullet to his ear at point blank range.
Was it a robbery gone wrong? An assassination? Or was it the violent culmination of a love triangle fuelled by jealousy, suspicion and many, many gin and tonics?
For months, Josslyn Hay, the 22nd Earl of Erroll, had been engaging in a very passionate, very public affair with Lady Diana Caldwell, the much younger new bride of Sir "Jock" Delves Broughton.
Extra-marital affairs were part of life in the hard-partying, fast-living Happy Valley set, who were seemingly immune to the conventions and tragedies of the day.
While their compatriots fought on the battlefields of Europe, and British colonisers exploited Kenya's natural resources with devastating consequences for locals, the Happy Valley set existed in their hedonistic oasis, partying, drinking and sleeping with each other's spouses.
But the murder of one of their own pierced the group's sense of invincibility.
Worse still, Sir Jock was arrested a few weeks later, accused of hunting down the rival for his wife's affections, and killing him in cold blood.
Britain was transfixed by the trial, with its twists and scandalous revelations, including Sir Jock's admission that he and Lord Erroll openly discussed their love triangle.
"Diana tells me she is in love with you," Sir Jock recalled saying to Lord Erroll.
"She never told me that," he allegedly retorted. "But I'm frightfully in love with her."
The trial lasted a month in a hot, stuffy Nairobi courtroom, with a servant testifying that he saw Sir Jock handling two pistols shortly before the murder, while another said he lit a bonfire in the backyard of his estate the day after the crime.
The murder weapon was never found, and Sir Jock was inevitably acquitted by a jury of his peers.
The mystery of who killed Lord Erroll was never solved.
For more than 84 years, outlandish theories about the murder have swirled, with some convinced it was Lady Caldwell herself, while others believe it was political figures who assassinated Lord Erroll because of his fascist connections.
But a secret recording unearthed decades after the shooting might finally unmask the killer.
Two aristocrats move to Africa and fall in with a mysterious set
Before Lady Caldwell met Sir Jock, she was a widely admired socialite moving in aristocratic circles and collecting suitors like precious diamonds.
The daughter of a wealthy gambler and a famous beauty, Lady Caldwell was a master of anything she put her mind to: dancing, horseriding, even flying complex aircraft.
"[Diana was] one of those creamy ash blondes of the period with a passion for clothes and jewels, both worn to perfection, and for enjoying herself and bringing out enjoyment in others," said writer Cyril Connolly.
She was a regular fixture in Tatler magazine, dazzling photographers on last-minute sojourns through Europe or on London's famous party scene.
Bold, charismatic and beautiful, Lady Caldwell worked at the Blue Goose, a cocktail bar in Mayfair that served as the perfect place for women to meet well-bred, eligible bachelors.
She had her pick of possible husbands, but her first marriage to playboy musician Vernon Motion ended as abruptly as it began.
The pair divorced within two weeks of their nuptials on the grounds of adultery.
More suitors and proposals followed until she eventually set her sights on a man 31 years her senior.
"[Sir Jock] seemed much older than other men, who thought him rather odd, a little sad," a 21-year-old unnamed attendee of the 400 Club in Leicester Square told White Mischief author James Fox.
In 1939, Sir Jock's wife fell in love with an English lord and filed for divorce, leaving him free to marry Lady Caldwell.
In many ways he was her opposite. Where she was charming, he was distant and haughty.
She liked to party, fly planes and laugh. He was more of a loner, had few hobbies and was humourless.
There was also the significant age gap between them. Lady Caldwell was closer in age to Sir Jock's son than she was to him, an issue that became a point of tension within the family.
But Sir Jock defied the sceptics and married Lady Caldwell. In 1940, he moved to Kenya with his new bride after amassing large debts in London.
He had been a frequent visitor to the British colony since his youth, having bought large parcels of land and a coffee plantation in Nairobi in 1923.
In "Masai country", home to a semi-nomadic ethnic group for hundreds of years, a young Sir Jock had been told by a doctor he would find a cure for his headaches.
Now he hoped to find a new lease on life and a refuge from the horrors of World War II.
The couple settled near Nairobi and soon moved within the hedonistic social set of British and Anglo-Irish aristocrats living in the Happy Valley.
Friends had warned Sir Jock that his wife would attract attention in their new home, particularly among other expats likely to be drawn to her energy, youth and charm.
But he had shrugged it off, Fox writes, telling them he wasn't the least bit jealous.
Within weeks of their arrival, Lady Caldwell embarked on a love affair with a man much younger than her husband.
His name was Lord Erroll.
A complicated love triangle ends in murder
Like every other member of the Happy Valley set, Lord Erroll moved to Kenya in search of something more than the immense privilege to which he'd been born.
He wanted freedom.
Lord Erroll may have inherited a prestigious earldom, but his family left him no wealth.
He was supposed to follow his father into a life of diplomacy after being accepted to work at the Foreign Office, but instead Lord Erroll fell in love with an older woman.
Over the course of her unconventional life, Lady Idina Sackville would marry and divorce five times.
She had a dog named Satan. She threw swinger parties. She nicknamed her bed "the battleground". She eventually inspired Taylor Swift to write a song about her.
Lord Erroll, 22 to her 30, was infatuated.
The scandal of their marriage prompted the newlyweds to pack up their belongings and start again in the Happy Valley, where they could be free of the constraints of upper class society and live off Lady Sackville's considerable wealth.
For nine years they were happy together, throwing legendary parties in their bungalow on the slopes of the Aberdare Range, accumulating more and more debts, until finally, she filed for divorce, alleging financial misconduct.
Once again single, Lord Erroll continued his hedonistic ways, bedding wives and playing polo at the Muthaiga Country Club.
"To hell with husbands," was reportedly his motto in life.
So when he met Lady Caldwell at the club, it didn't seem much of an impediment that she had only married Sir Jock six months before.
The two began a passionate affair, hiding it from no-one, since extramarital relationships were all but encouraged in the Happy Valley set.
If Sir Jock was jealous of his wife's flagrant cheating, friends say he gave no sign.
Three months into the affair, Lady Caldwell dined with her husband and her lover, before they left Sir Jock alone so they could go out dancing.
Lord Erroll dropped her home in the early hours of the morning, and then drove off alone in his Buick.
His body was later found with a bullet wound suggesting he'd been shot from behind while he drove.
There were also strange, unexplained white scuff marks in the boot of the car.
While no murder weapon or other physical evidence was found, police concluded there was only one man with the motive to kill Lord Erroll.
The African murder trial that transfixed Britain
Sir Jock was arrested several months after the shooting, and stood trial in Nairobi on May 26, 1941.
While police were convinced he was the killer, the Happy Valley set were unsure, pointing out that Lord Erroll had plenty of enemies.
"Some commentators suggested that it was Diana who shot her lover when he tried to end the relationship; others that [the Earl of] Erroll was murdered by one of his other jealous lovers, or a cuckolded husband who couldn't bear the shame," wrote author Christine Nicholls in her book Red Strangers: The White Tribe of Kenya.
Lord Erroll was a member of the British Union of Fascists leading some members of the Happy Valley set to wonder if his murder was more political than personal.
"There have even been claims that Erroll's death was due to a secret service conspiracy, and that he was executed because he was suspected of collaborating with the Germans in wartime and belonged to a renegade group including the Duke of Windsor and Rudolf Hess," Nicholls wrote.
"People have always been enthralled by this mystery."
But Kenyan police believed the simplest explanation was the most likely: Sir Jock, humiliated and lovelorn, snuck out into the dark and confronted his wife's lover with a pistol.
There was only one problem. They couldn't find the gun that killed Lord Erroll.
An autopsy suggested he was killed by a bullet with five grooves, fired by a pistol with clockwise rifling.
But Sir Jock's only pistol was a Colt with six grooves, which fired bullets anti-clockwise.
He told police that he had — perhaps conveniently — been robbed of his other weapons just days before the shooting.
Sir Jock also had an alibi for the time of the murder, which took place some time after 2:30am.
He claimed he was 3.8 kilometres away, checking in on his neighbour June Carberry, who was known to be a heavy drinker.
Sir Jock had a limp, so it was concluded he could not have travelled the distance between the crime scene and Ms Carberry's house to commit the murder.
Sir Jock reportedly testified for 22 hours, telling the jury Lord Erroll was "a very great friend, whose brain and sense of humour I admired".
After a month-long trial, Sir Jock was acquitted.
But while he was free, Sir Jock was never welcomed back into the Happy Valley set, and Lady Caldwell had already moved onto another lover.
He sailed back to England alone.
Days after he arrived, he was found dead from an apparent suicide in an upscale Liverpool hotel.
Meanwhile, Lady Caldwell continued to amass husbands, lovers and riches in Kenya, until she was considered the most powerful European woman in Africa.
What happened to Lord Erroll?
For more than 80 years, it seemed as if the question of who killed the earl on that empty road in Kenya would never be answered.
With the prime suspect, Sir Jock, dead, and few other strong leads for the Crown to pursue, the murder of Lord Erroll was declared a cold case.
Lady Caldwell married one month after her husband's death, this time to a friendless cattle rancher in Kenya.
Her reputation had been marred by the scandal, but she slowly recovered her social position through her relationship with Gilbert Colville.
He was the richest landowner in Kenya and she, as his bride, became a very powerful figure in the country as well.
The couple were together for 12 years, until they went their separate ways in 1955.
Her fourth marriage was to Thomas Pitt Hamilton Cholmondeley, 4th Baron Delamere.
"I had years of happiness with Tom. We used to talk to each other for hours at a time," Lady Caldwell told Fox of her last husband.
After his death, she moved back to the UK and died of heart failure at the age of 73.
Many believed she took the clues of who was behind the murder to her grave.
"With her death, history has been robbed of the last witness to the events surrounding the murder of her lover, Lord Erroll," Fox wrote in London's Daily Telegraph newspaper.
But in 2007, there was a surprising breakthrough in the Lord Erroll murder case.
Nicholls told the Telegraph she had found evidence that suggested Sir Jock was the killer all along.
Mary Edwards, the wife of the former deputy high commissioner in Kenya, had given Nicholls material related to the case, including tapes of interviews dating back to 1987.
One of the recordings was of a man whose parents were farming partners with the family of Ms Carberry, the woman who had been Sir Jock's alibi.
He claimed on the night of the murder, Sir Jock had hidden inside Lord Erroll's Buick, while he was escorting Lady Caldwell home after they went out dancing.
Sir Jock was allegedly wearing white plimsolls, which is why police found scuff marks in the car.
As Lord Erroll was making his way to the main road, it's believed Sir Jock struck.
The man in the recordings claimed Sir Jock had arranged for someone to pick him up further along the road at a pre-arranged spot.
"The tape recording I have gives the name of the driver who collected Delves Broughton," Nicholls told the Telegraph.
"The driver was Dr Athan Philip, an ear, nose, throat and eye specialist who was a refugee from Sofia in Bulgaria. He was a neighbour of Delves Broughton and his practice wasn't going very well, so he was happy to take a generous payment for doing a pick-up."
While the mystery of who killed Lord Erroll now appears to be solved, the details of the case continue to capture interest decades later.
The Happy Valley set slowly disbanded, as aristocrats returned to their home countries, or moved to other parts of Africa.
During their reckless lives, members of the group were ignorant to the plight of the locals whose land they had colonised.
But beneath the surface, a rebellion was simmering.
In 1952, the Mau Mau Uprising began, in which local fighters tried to overthrow the Europeans occupying their country.
The rebellion was brutally put down by the British Army through public executions, detention programs later described as gulags, and torture.
But in 1963, Kenya finally attained independence, and the vast majority of white settlers were gone by the end of the decade.
