A former teacher has been told to expect jail after admitting blackmail and sex offences.

Samuel Alexander pleaded guilty to a string of offences when he appeared at Amersham Crown Court this morning.

The 24-year-old, of Speen Road, North Dean, admitted to two counts of sexual assault, two of blackmail and one of attempted voyeurism during today's hearing.

He also pleaded guilty to a charge of distributing an indecent image of a child, relating to a posting he made on his victim's Twitter page.

Alexander denied a further sexual assault charge and one of possession of an indecent image of a child, with prosecutors indicating they would not proceed with those counts.

All of the charges relate to the same female victim, who cannot be named for legal reasons, and some date back to 2008.

The court heard Alexander has resigned from his position as a teacher since the offences came to light.

He will return to court to be sentenced on July 17. He was granted bail, with a condition to report to High Wycombe police station each day.

Judge Francis Sheridan banned Alexander from working with children and made him the subject of an interim sex offenders' registration requirement ahead of his next court appearance.

The judge said: "I will say custody is inevitable in this case - it's just a question of how long."