Wiltshire Police has apologised to a 59-year-old woman after a custody sergeant was convicted of assaulting her.

CCTV caught Sgt Mark Andrews dragging Pamela Somerville across the floor at the Melksham custody suite and shoving her into a cell. She had been arrested after being found asleep in her car.

He was convicted after a trial at Oxford Crown Court of assaulting her causing actual bodily harm in the incident two years ago and on Tuesday he was jailed for six months.

Andrews, who is expected to be sacked, was charged after the incident was reported by another officer.

Asst Ch Const Patrick Geenty said the force respected the decision of the court and had formally apologised to the victim.

He said 30,000 people had been through custody since the incident and of 13 complaints of assault, none had been substantiated.

However he said unlawful use of violence by officers would not be tolerated. "This incident should not have happened and I am very sorry that we let this lady down. Although she had been lawfully arrested, she was not charged with any offence," he added.

Christopher Hoare, Chairman of Wiltshire Police Authority, endorsed Asst Ch Const Geenty’s statement and said: "On behalf of Wiltshire Police Authority, I would like to express our own regret to Pamela Somerville for the assault she suffered while in police custody at Melksham Police Station in July 2008." He said the authority had been involved in implementing new custody procedures and would consider carefully the court’s findings and take any further action needed