THE detective who led the Sian O’Callaghan murder inquiry has quit his job at Wiltshire Police 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 the 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meant vital evidence in the Becky Godden-Edwards case was ruled inadmissible and led to the charge for her murder being withdrawn.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 Mr Fulcher had a case to answer over breaches of the Police and Criminal Evidence Act and in ignoring force orders in disclosures to the media.

These were put to him at a force disciplinary hearing in January, when an independent panel of senior officers 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 yesterday 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.”

Becky’s mother Karen Edwards reacted with shock at the news.

The 52-year-old said: “I feel that this is going to be such a waste from such a wonderful, experienced detective.

“He is and will always be my hero and I will always be eternally grateful.

“I have such admiration for him, I have said it many times before if he had stuck to PACE rules then neither my daughter Becky or Sian would have been found.

“We all know that the rules say once Halliwell had confessed to Sian’s murder he should have been taken straight back to the police station.

“Becky would never have come into the equation, and Sian would have never been recovered from where she was found.

“Steve Fulcher gave two families back their two daughters and we were able to put them to rest.

“This makes the changes in the PACE rules even more needed now, had our rules been different none of this would be happening.

“I have been in contact with other families that Steve Fulcher has helped over the years in solving very difficult murders and they feel the same as I do, without him they might have never buried their family member.

“I would like to thank Steve Fulcher from the bottom of my heart for all he has done for us.”

Mr Fulcher, who has a degree in criminology from the University of Cambridge, joined Sussex Police in 1986 before moving to Wiltshire in 2003.

In Sussex he was involved with the Sara Payne murder inquiry, and in Wiltshire, as a senior investigating officer, he has been in charge of a number of high-profile murder investigations.

Eamonn Caroll, the assistant secretary of the PSAEW, called the detective a dedicated officer.

He said: “The Police Superintendents’ Association is aware of the decision of DSI Steve Fulcher to resign from Wiltshire Police.

“The association supported Steve Fulcher when he was under investigation by the Independent Police Complaints Commission and at his subsequent disciplinary hearing.

“He was a dedicated police officer who had a lot to offer the police service.

“In light of his decision, we wish him well for the future.”