Josslyn Hay was tall, blond and 22 when 30-year-old Idina married him in 1923 after amicably divorcing her second husband, Charles Gordon. Joss was serially unfaithful from the start. Idina professed not to mind. In any case, she openly shared Joss with another woman, an American called Alice Silverthorne.

Idina began to rely on Alice to return Joss to her, and Alice relied on Idina’s acquiescence whenever she and Joss had a fling. Gradually the two women became friends, waiting together for him to return from whichever third bed he had slipped off to.

Golden-maned, with strong, aquiline features, Joss had a direct gaze and thick, wide lips. His grandfather was the Earl of Erroll, the hereditary Lord High Constable of Scotland. When he and Idina bought a farm halfway up a mountain in Kenya and built a house, he insisted on calling it Slains after his ancestral home, Slains Castle, which had recently been sold to meet family debts.

There they held parties for friends, who, on arrival, bathed, slipped into silk pyjamas, were handed a cocktail and were ushered through into the memsahib’s bathroom. There Idina lay simmering in green onyx, ever-present cigarette holder and crystal tumbler on standby, welcoming them in.

She chattered as she washed, climbed out, dried herself and dressed. A gramophone would be brought in, its handle wound, a record put on – the latest jazz arrived from England with Idina’s pile of books – and off they went, dancing in pyjamas almost as soon as the sun had set. Formality broke into the evening with dinner, a four-course French feast washed down by whisky. Cocktails again.

The alcohol and altitude together sent them as high as kites, with almost no need for the odd line of cocaine. And then she started the games. These were a way for Idina to exercise some control over Joss’s lovers. He did not drink alcohol, saying he did not want “to impair my performance”.

They started with word games, charades, a bit of acting, singing, then more dancing to the gramophone. More alcohol. Then back to Idina, standing in front of the fire, a long, black cigarette holder at her lips.

The bedrooms were locked. Idina spread the keys on a table and with the roll of dice, the turn of a card, the blow of a feather across a sheet stretched between the guests’ trembling hands, each would win a new key and partner for the night.

The marriage, of course, did not survive. Joss fell in love with another man’s house – and stole his wife in order to get it. After the divorce he and Idina remained friends. Both had numerous lovers; Joss inherited the family title; and Idina married twice more. Her games continued, and earned the area and its upper-class settlers the name of Happy Valley.

A month or so before Christmas 1940, a wealthy newcomer, 57-year-old Sir Jock Delves Broughton, arrived with his young wife, Diana, his former mistress. Almost immediately Joss started an affair with her.

At first they were reasonably discreet. But by early January 1941 they no longer appeared to care. They clung to each other for hours at a time on Nairobi’s plentiful dancefloors. On the morning of January 24 Joss was found dead in his car near a crossroads a few miles outside Nairobi. He had been shot in the head.

In 17 years in Kenya he had had affairs with many of the women there, nearly all of whom had retained a soft spot for him. Barely a female eye at the Muthaiga club outside Nairobi was dry. Alice, who had shared him long ago with Idina, immediately attempted suicide.

She recovered, and when Jock Delves Broughton was tried for Joss’s murder, Idina and Alice turned up each day, dressed to the nines. They sat in the gallery and hung on every word of evidence given, as their lives were pored over, scribbled down by court reporters and wired back to London and New York, where readers lapped up what was known as the White Mischief trial.

Jock was acquitted, and Joss’s murder declared unsolved. The drama of the trial had, however, been too much for Alice. She asked her houseboy to make up her bed with a set of extraordinarily ornate lace and linen sheets. Then she lay down, stuck the end of a revolver in her mouth, and shot herself.

Idina’s once Happy Valley was now truly over. She lived on, had more lovers and died in 1955 at the age of 62. She had never wanted to be an old woman – and it seems she had got her way.

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