Two guests arrived late, missing out on most of the fun. They were a pair of 17-year-old showgirls called Mandy Rice-Davies and Christine Keeler. To Mariella and her friends, Mandy and Christine were known as "Stephen's popsies". Stephen Ward was a purveyor of pleasure, and kept a stable of young women eager to meet rich men. This occupation guaranteed his usefulness to high society, and, it would later emerge, to MI5. But his social and political usefulness started as a private passion. He found the popsies in station cafes, he told Hod. He would ask if they were models, and then sketch portraits of them to put them at their ease. He always had a sports car parked around the corner. No one was to know it was on hire purchase. The girls usually came from the provinces, and were still in their teens. They had come to London to hit the big time. Stephen would offer a place to stay and then deliver an intensive grooming regime before introducing them to delicately placed men. The rest was up to the girls, he told them.

Not even Stephen had ever met a girl like Mariella. She fascinated him, Christine wrote in her memoir. Like Athena, she had arrived on the London scene fully formed, as though hatched from Zeus's thigh. Hod had snapped her up while she was still a topless dancer. Unlike Stephen's girls, Mariella was cultured, had intellectual leanings and was mysteriously "Eurasian" in appearance. The inscrutable air she cultivated added intrigue to her slanting eyes and haughty bearing. And she wasn't just a pretty face. She told exotic stories about a runaway communist and a fairytale castle in Prague, where her childhood was spent. In the former territories of the Austro-Hungarian empire, in the aftermath of war, her portrait, she claimed, was "engraved on the nation's banknotes, and [her] birthday declared the Czechoslovakian National Day of celebration". It was hard to remember she was born in Sheffield, which was exactly what she wanted. Christine and Mandy, from Staines and Solihull respectively, were just as lovely but more straightforward. They were classic products of Stephen's tried and tested finishing school. Six months previously, Hod had spent the evening at Stephen's flat in Wimpole Mews, W1. He told Mariella what he had witnessed. 

"Hod watched Christine serve dinner," Mariella recorded. "Ward had finished training her, but to test her ability instructed her to cook, lay the table correctly, and eat with them. Hod related to me her lapses, and how Ward told her not to sprinkle salt on her food. She obediently poured a small amount on the side of her plate. Several such mistakes were criticised by Ward — he wanted to impress Hod with his teaching technique." 

Both men saw themselves as Pygmalion. But how much Hod contributed to the finished article of Mariella remains, like everything about her, a mystery.

The party was virtually over by the time Christine and Mandy arrived. Stephen had telephoned them to suggest they come along after he had been caught in the bedroom on his knees. In fact, Mariella almost fell over him as she was groping around in her shoe cupboard. On closer inspection she saw that Stephen was holding one of her stilettoes over his nose and mouth, leaving his other hand free. Normally, she observed, Stephen was a watcher rather than a doer. But on this occasion he was "huffing and puffing with excitement". He asked Mariella to put her highest heels on and stand on his scrotum.

Once he had recovered, he made the phone call. In an interview, Mandy recalled: "Stephen met us at the door, wearing nothing but a sock. I thought it was a joke. Everyone was in deshabille, and Mariella was there wearing a kind of black corset, and carrying a whip. Naked people were everywhere, draped over chairs, or standing around laughing and joking.

"I didn't know where to look," recalled Mandy. "After all, I was only seventeen, even if I had been around. I remember spotting this plate of tangerines — they were a rarity in winter in those days — and I attacked those tangerines and some chocolates until I felt sick."

While she devoured rare treats, Mandy could not help noticing that her hostess was in bed with six men. Christine got up close to investigate. Mariella "had a tiny waist that exaggerated her ample figure. She was a siren, a sexual athlete of Olympian proportions — she could do it all. She knew all the strange pleasures that were wanted and could deliver them."

And then there was the man in the mask still cowering under the table.

"The man in the mask was a masochist," wrote Mariella, "and asked me to treat him as my ‘slave'. I willingly agreed, and caused him mental and physical pain. This was what he wanted — I did nothing against his wishes. The humiliation he underwent was extreme, but was the dream of his life." The man made Mariella promise to keep his identity secret. This she did, even after his death four years later, in 1965.

In fact, it was not until 1987, four years after Mariella's death, that Hod indicated that the man in the mask might have been the Honourable Anthony Asquith, youngest son of a Liberal Prime Minister, the First Earl of Oxford and Asquith. Anthony Asquith had the added distinction of being one of Britain's most successful film directors. His films included a 1938 adaptation of Pygmalion, a storyline that also occupied the imaginations of Hod and Stephen Ward. Other films were The Winslow Boy, The Browning Version and The Yellow Rolls-Royce. Asquith's cinematic successes were stellar. He was a fellow of the British Academy and Governor of the British Film Institute. To his overbearing mother, he was simply "Puffin".