The detective who led the Sian O'Callaghan murder enquiry has resigned from his post months after being found guilty of misconduct.

Detective Superintendent Steve Fulcher led the investigation into the popular 22-year-old's disappearance from Old Town in March 2011 and subsequently secured a conviction of her killer Chris Halliwell, 50, of Ashbury Avenue, Nythe.

But he faced disciplinary action after a judge ruled his unorthodox interviews of the mini-cab driver, at Barbury Castle and Uffington, without cautioning him meant vital evidence in the Becky Godden-Edwards case was ruled inadmissible and led to the charge for her murder being withdrawn.

An Independent Police Complaints Commission report found that DSI Fulcher, hailed as a hero by Becky's mum Karen Edwards, had a case to answer to over breaches of the Police and Criminal Evidence Act.

These were put to him at a force disciplinary hearing in January, when a panel of independent officers from other forces resolved to find him guilty of two counts of gross misconduct. But he was allowed to keep his job after he was given a final written warning by the force.

A spokesman for Wiltshire Police today said: "Wiltshire Police can confirm that Steve Fulcher has resigned from his post in the Force. It would be inappropriate to comment further on this matter."