The 51-year-old frontman stunned the jury at Minshull Street Crown Court when he was revealed as a prosecution witness today.

Brown said that Talbot, 65, taught him biology during his time at Altrincham Grammar School between 1974 and 1979.

And saying that he had “nothing to gain” from lying and was supporting his classmates, the musician claimed Talbot showed children a video which he later “later realised was probably a gay porn film”.

Fred Talbot arrives at Minshull Street Crown CourtTalbot denies 10 offences of indecent assault on five boys while working as a teacher in the late 1960s and early 1980s before his TV career took off.

Recalling one alleged incident when he and his fellow classmates were 11 years old, Brown said Mr Talbot “asked all the class if any of us had ever masturbated”.

“He went on to explain how to masturbate, how you should masturbate and the following lesson he asked who had masturbated.”

Brown said pupils responded with “nervous giggles”, before some boys raised their hands. He said that in further lessons, Talbot approached the boys who had raised their hands and “murmured” in their ears.

On a separate occasion, the singer said Talbot took the class into a room with a projector and showed them a film “of a guy walking into a room dressed in denims, sits on bed, takes trousers down and masturbates”.