SINGAPORE — He had paid for her services “upfront”, which was a “rare thing” for her, and their sexual encounters took place at “four- to five-star hotels” instead of the usual “budget hotels”.

These made former UBS Executive Director Juerg Buergin — who is alleged to have had commercial sex with an underage prostitute — a memorable client, the court heard yesterday.

Testifying in-camera, the girl, who recently turned 20 and cannot be named due to a gag order, cited several anecdotes in confirming that Buergin had been her client.

According to the girl, Buergin was the only one out of the 80 men the girl slept with who had placed the money in the hotel’s envelope, said Deputy Public Prosecutor Kavita Uthrapathy.

The girl also said she had provided sexual services to fewer than three “white guys”.

The Swiss national, 41, who is married with two children, allegedly had sex with the then-underage girl known as Chantelle on Sept 29, 2010, at Shangri-La Hotel, and on Jan 3, 2011, at Mandarin Oriental Hotel, paying up to S$650 for each session.

He is the first to claim trial in the high-profile online vice ring scandal and is fighting to prove that he had been cheated by the pimp, Tang Boon Thiew, 39, who he alleged had misrepresented the girl’s age.

During the three-hour private court session, several members of the public and the media tried to get a glimpse of the girl through the glass panels of the court door, which had been covered with paper, but were turned away by security guards.

The court also heard that Buergin, who used the moniker Robert James in SMS exchanges with Tang, had been a regular client who met up with at least 10 escorts he assumed to be aged between 18 and 43 years old for sexual services.

A total of 17 escorts had been requested or recommended by Tang, including Chantelle.

During cross-examination, Tang admitted that the escort website where Buergin came to know about Chantelle had stated that she was an 18-year-old “polytechnic student” and a “Barbie girl” who was “new to the escort trade”.

Tang said he had told Buergin that Chantelle was 18 but that he was “not aware” that she was underage when Buergin first engaged her. Tang also claimed that he had not known — even upon knowing the girl’s real age — that it is illegal to have paid sex with a girl below 18.

The trial will resume on Monday.