A geography teacher who had a nearly four-year sexual relationship with an underage pupil has been banned from the profession for life.

Suzanne Harrison, 46, became friends with one of her students (Pupil A) and her family while teaching at Philip Morant School in Colchester.

Their sexual affair began in early 2006 when Ms Harrison was minding Pupil A, then aged 15, and her sister while their parents were out.

In late 2009, Ms Harrison introduced the girl to her then-partner, who subsequently began a relationship with the pupil.

When told of Pupil A’s previous relationship with her teacher, the new partner reported it to the girl’s mother and they went to the police.

Ms Harrison was arrested in July 2011 and swiftly resigned from her post. The following month she pleaded guilty to child sex offences in Ipswich Crown Court and was detained in hospital.

The Teaching Regulation Agency (TRA) heard Ms Harrison had a good history in her job and many colleagues, parents and pupils spoke warmly of her.

However, it said the seriousness of her offences - which the panel described as a “double breach of trust” - warranted a ban without review.

“The panel noted that the behaviour involved in committing the offence involved the most severe breach of boundaries, not only as a teacher, but also as a friend of Pupil A’s family,” it said.

“There is a strong public interest consideration in respect of the protection of pupils given the serious findings of an inappropriate sexual relationship with a pupil.

“The panel makes a recommendation to the Secretary of State that a prohibition order should be imposed with immediate effect.”

Decision-maker Dawn Dandy agreed, and banned Ms Harrison from teaching indefinitely. She was given 28 days to appeal the order.