Television weatherman Fred Talbot used his "boundless energy" and "extrovert personality" to help gain the affection and trust of five schoolboys he indecent assaulted, a jury has heard.
Talbot, 65, is said to have assaulted his victims between the late 1960s and the early 1980s during his former career as a teacher.
Four of the complainants were teenage pupils at Altrincham Grammar School for Boys, where Talbot taught biology.
Talbot, who was a regular on the floating weather map in Liverpool's Albert Dock for ITV's top-rating This Morning show, denies 10 counts of indecent assault.
Opening the case at Manchester Minshull Street Crown Court, prosecutor Neil Usher said: "The very qualities that made Fred Talbot so successful as a TV celebrity - his boundless energy, his infectious enthusiasm, his extrovert personality - helped him gain, we say, the trust of these boys.
"Trust, which the prosecution say, Mr Talbot repeatedly abused when, away from their parents on school trips organised by Mr Talbot, he sexually assaulted each of them.
"We say that when it came to teenage boys in his care, Fred Talbot was something of a 'chancer'.
"One of these men who regularly and repeatedly tries it on with his intended victim as often as he can in the hope that his sexual advances will not be rejected.
"Or, at the very least, the sexual advances will be met by a passive response due to confusion, fear, intoxication or youthful inexperience of how to react when being placed in such an unusual, shocking and, no doubt on occasion, frightening position."
The jury of nine women and three men were told that many if not all of them would know the defendant as "Fred the Weatherman".
He had appeared on local and national television since the mid-1980s until recently, and has appeared in various other ITV programmes, the court heard.
Mr Usher said the allegations centred around two periods of time - when Talbot was a trainee teacher in Newcastle in the late 1960s and early 1970s and from the mid-70s to 1984 when Talbot taught in Altrincham.
The prosecutor said Talbot says nothing sexual or even inappropriate occurred between himself and the Altrincham pupils, while he states that sexual activity with the complainant during his teacher training only happened when the boy turned 16.
The latter complainant said he first met Talbot when he visited his school in Gateshead and was someone who came from a very poor background.
Mr Usher said: "Meeting Mr Talbot meant he was able to go places and do things and meet people he would never have been able to had the defendant not taken him under his wing."
Within weeks, the boy was invited to visit Talbot at his accommodation and it later led to the pair sharing a bed with Talbot "pushing and manoeuvring himself against him" in a sexual manner, he said.
It was the boy's first sexual experience, added Mr Usher, which left him very confused.
There were more overnight visits Talbot "gained in confidence and stepped up his sexual advances", said the prosecutor.
The court heard that the complainant is clear that the defendant never forced himself upon him but described Talbot coaxing him into letting perform sexual acts on him.
On one occasion he recalled, when still aged 15, he went to a ball at Talbot's teacher training college with a girl and later the defendant performed a sex act on him outside.
The next complainant claimed he was sexually assaulted by Talbot in the mid-1970s on a barge during a canal trip organised by Altrincham Boys Grammar School.
He said Talbot was the teacher in charge and each night one of the schoolboys had to sleep in a double bed with him as there were not enough bunk beds for everyone.
Talbot sexually assaulted him in the bed, he alleges.
Mr Usher said the teenager was one of a number of former pupils who described how Talbot managed to gain their trust and affection.
He said: "He said that he was good at befriending you, making you feel like he was your mate, a friend more than a teacher. An approach the prosecution says was quite deliberate on the part of Mr Talbot, given his objective of gaining the trust of these boys."
The third complainant said he too was indecently assaulted in the mid-1970s by Talbot in his double bed on the barge during a weekend canal trip.
He said he was drunk after Talbot took older boys to the pub and later brought beer back to the boat.
Mr Usher said: "He recalls Mr Talbot suggesting that some of the boys pretend to be girls so that they could, as he put it, have an 'orgy' which had to be kept secret. He recalls the boys and Mr Talbot all taking their clothes off and rolling around."
The jury heard that this complainant previously contacted police in 1992, 1996 and 1998 to say that Talbot had sexually abused him but the defendant denied the allegations and police decided there was insufficient evidence to prosecute.
The alleged victim admitted that when he went back to the police in 1996, he exaggerated the events of the sexual abuse in frustration at the case not going forward, Mr Usher said.
The trial continues.