A chemistry teacher on a school trip to Cuba had drunken sex with a diving instructor whilst supposedly looking after pupils, a conduct hearing was told.

Hayley Dimmock, 28, was banned from teaching indefinitely after also admitting allowing a male pupil from Bedford School to run his hands up her ankle and inner thigh, touch her bottom and put her iPod in the front pocket of her shorts.

The 'young and inexperienced teacher' then drank at a party and went to a diving instructor's room to have sex instead of making sure pupils were safely back in their rooms, it was said.

Two members of staff passing the room were able to see what was happening through a gap in the curtains and had to stop pupils walking past.

She received four formal warnings about her behaviour on the trip in July 2014 but spent half an hour alone with the pupil at his home after returning to the independent boarding school, which was founded in 1552 and charges fees of up to £9,654 per term.

Ms Dimmock, who studied at the University of Bedford, started work at the school in September 2012 but was fired in November last year after an investigation by the school's head of science, who had been on the trip.

He found Ms Dimmock and the pupil had 'too much physical contact' and suggested she had been 'intimate with him for a while'.

A biology teacher also said they 'witnessed Ms Dimmock undertaking "intimate whispers", private conversations and general touching with the pupil'.

In a statement to the teacher's watchdog, the National College for Teaching and Leadership's professional conduct panel said she had been depressed after a relationship ended and felt her colleagues did not assist her during the trip.

Ms Dimmock admitted the relationship with the colleagues deteriorated and said she spent most of her time with pupils and dive staff. 

She added the 'liaison' with the instructor had left her 'embarrassed'.

On banning her, the panel said: 'By Ms Dimmock's own admission she spent the night in the diving instructor's room and therefore could not be supervising students.

'The panel found that Ms Dimmock's conduct was a clear failure to safeguard and supervise students under her care. Having sexual relations whilst she was meant to be supervising students was a failure to adhere to professional boundaries.

'In addition, Ms Dimmock staying overnight in a room that was located close to students' accommodation was also a clear failure to act within or adhere to professional boundaries, as it was possible that Ms Dimmock could have been seen or heard by students.'

Her drinking and having sex 'could have led to students being exposed to or influenced by her inappropriate behaviour in a harmful way' and it ruled she had overstepped her 'professional boundaries'.

She can apply to be reinstated on the teaching register in three years.