A man has told the trial of former TV weatherman Fred Talbot he felt "shocked" and "repulsed" after being indecently assaulted in his tent on a school camping trip as a teenager.
The witness told a jury he "froze" after Talbot, then a teacher at his school, carried out the night time assault during an excursion to the south of Scotland in 1979.
"I thought this a betrayal of trust by somebody I regarded as a friend," the man told Lanark Sheriff Court.
Talbot, 67, from Bowdon, is on trial accused of indecently assaulting several teenage boys on school trips to Scotland.
He is also accused of lewd, indecent and libidinous practices and behaviour towards a boy aged 12 on a trip.
Talbot denies the charges against him.
The witness, the first to be called at the trial, told the court he was a pupil at a grammar school in Cheshire in the 1970s, where Talbot was a teacher.
The man, who cannot be named for legal reasons, described how he went on a weekend camping excursion led by Talbot to Grey Mare's Tail, near Moffat in Dumfries and Galloway, in the spring or summer of 1979.
The witness, now 54, said the group of boys on the trip had been allowed to buy alcohol and the atmosphere was initially "happy" and almost "joyful".
Talbot was more informal than some other teachers and would talk about subjects such as sex, the court heard.
The witness told jurors that, at bedtime on the second night of the trip, Talbot asked if he could join him in the tent he was sharing with a friend because it had more room.
The man said he had "slight reservations" at the time but agreed because "I thought he was my friend, I thought nothing would happen".
Talbot then brought his sleeping bag into the tent and laid down between the boys, the court was told.
The witness said he then remembered the accused putting his hand into the opening of his pyjama bottoms and started trying to masturbate him.
"I was shocked at the time so I just froze for a moment," he said, before describing how he moved the accused's arm away.
Asked by prosecutor Imran Bashir how he felt, the witness replied: "Shocked, repulsed. I also felt foolish to let myself get into this position."
He went on: "I thought this a betrayal of trust by somebody I regarded as a friend. I felt upset about it."
The man said Talbot later tried to apologise to him, but he told jurors: "I thought 'this isn't an accident, this is something you've deliberately done'."
He told Mr Bashir: "It was an assault in my mind," and he agreed that it had been of a sexual nature.
Alan Grevelle, defending, suggested to the witness that he had reacted to the alleged incident in a "measured" way at the time. The man rejected the suggestion and said he had been "too frightened" to do anything else.
The lawyer put it to the witness he had "jumped on the bandwagon" after seeing a media report about Talbot.
"I'm really sorry you had to say that," the witness replied.
Talbot is accused of carrying out the offences involving pupils aged 15-17 on trips in Scotland while he was employed as a school teacher.
He faces eight charges of indecent assault between January 1978 and November 1981 and one of lewd, indecent and libidinous behaviour in February 1978.
Six of the incidents are alleged to have happened on camping trips in Moffat, Dumfries and Galloway, and three on boating trips on the Caledonian Canal in Inverness.
The trial, before Sheriff Nikola Stewart, continues today, Tuesday.