A Grammar school music teacher embarked on an affair with a sixth-form pupil, a court heard on Tuesday.
Darren Caudle-Wood, a married 37-year-old of Church Road, Cheltenham, "kissed", "cuddled" and "touched" the girl, who was aged 17.
The pair enjoyed secret meetings after play rehearsals at Pate's Grammar School, the jury heard.
Mr Caudle-Wood denies seven charges of having sexual activity with a person under 18 while in a position of trust.
The girl, who cannot be named for legal reasons, was studying A-levels at Pate's Grammar School where Mr Caudle-Wood was director of music.
Gloucester Crown Court heard he invited her into his office for "little chats" to discuss music.
Prosecuting, Giles Nelson told the jury: "During the course of her first academic term, this defendant started to develop a specific interest in her.
"He would often invite her into his office for chats, which the prosecution say, started to strike a more intimate tone in his dealings with her."
By the start of the next academic year in September Mr Caudle-Wood could "no longer restrain" himself, he told the jury.
He hugged her "intimately" on her first day of the new term and started to put his hand up her blouse, it is alleged.
He later put his arms round her and kissed when they were alone after school."
A sexual relationship subsequently developed, it is alleged.
When he was arrested, the teacher said the girl was a "fantasist" and that his dealings with her had been professional.
The trial continues.