“One has to bear in mind that [the victim] is a vulnerable person and the degree of breach of trust by [Cheung] is deplorable,” Wong said in a 71-page judgment.

“In the present case, it seems to me that both blameworthiness and causative potency both point to the conclusion [Cheung] should bear the majority of the responsibility.”

The court heard that Cheung, now in his 60s, was charged in 2014 with having unlawful sexual intercourse with the woman. But the woman, then 21 and said to have the mental age of an eight-year-old, was unable to testify and the charge was withdrawn by the prosecution.

Judge Stanley Chan Kwong-chi said at the time that it was “the luck of the defendant but a misfortune to the victim or society” that prosecutors were forced to drop the case, despite what was said to be strong evidence collected by police.

The victim, now 31, was also unable to give evidence in the civil action, lodged by the woman’s mother in 2018.

Wong emphasised the importance of the court being able to determine “the inherent likelihood or unlikelihood of an event having happened, or the apparent logic of the events” in the case as the woman could not give evidence.

The prosecution is required to prove its case beyond reasonable doubt in a criminal case, a higher standard than required in civil proceedings.

The judge watched a video taken by a former resident of the care home that showed Cheung and the woman enter his office on August 10, 2014, the date of the alleged offence, and the warden closing the door.

Security camera footage showed the two were inside the room for about three minutes, where a sexual assault was said to have taken place.

Details of the assault were outlined by the victim’s mother and a care assistant who had been told of the assault by the victim.

But there was no evidence of the alleged assault and Cheung denied it happened during the civil proceedings and insisted he had only talked to the woman while they were in the office.

The woman was later examined by a specialist, who found she was suffering from psychiatric disorders brought on by a traumatic event.

Forensic reports submitted to the court suggested that tissue paper found in a rubbish bin in Cheung’s office contained his semen and the victim’s DNA.

But Cheung argued he had masturbated in a staff room and put the tissue in a bin there, which was later moved to his office in a bid to frame him.

But Wong said he gave “full weight” to the reports and dismissed Cheung’s testimony.

He added Cheung was a “dishonest witness” and his evidence did not stand up to scrutiny.

“I find that during the relevant period inside the office, [Cheung] had sexually assaulted [the victim],” Wong told the court.

He added that the care home management had “no proactive supervision” of Cheung and that there were no security cameras in his office.

Wong ordered a total of HK$1.19 million to be paid to the victim, with Cheung’s share amounting to 70 per cent, given the aggravated damage, the victim’s permanent incapacity and other factors.

He criticised Cheung and the care home for presenting an “an entirely unmeritorious” case and forcing the victim and her family to relive the experience.

Cheung was in 2019 convicted of five counts of indecent assault on a seven-year-old girl, who also had severe visual impairment, between 1982 and 1986.

The assaults happened when he was aged between 20 and 25. Cheung was sentenced to 33 months in jail.

His victim, by then in her forties, only reported the incidents to police in 2016.

The court heard at the time that Cheung had been a member of Hong Kong’s Paralympic Games swimming team and had won a bronze medal at the event.

He also won four medals at the Far East and South Pacific Games for the Disabled in 1982.