Sian O'Callaghan's body found after killer's admission
Amid the huge manhunt for Swindon office worker Sian O'Callaghan, a decision to ignore arrest guidelines by the detective leading the search proved crucial.
The move led Det Supt Steve Fulcher to pin Miss O'Callaghan's murder on Christopher Halliwell, but he had no idea it would also put him in the frame for killing Becky Godden, missing from the town for eight years.
It was an extraordinary admission by killer Christopher Halliwell to a detective, at a local beauty spot in Wiltshire, that proved key in the search for Miss O'Callaghan.
The 22-year-old had gone missing days before from a Swindon nightclub.
Despite identifying Savernake Forest for the search, being the last known place her mobile phone signal was traced, Halliwell's admission made it clear police teams were looking in the wrong place.
For Det Supt Fulcher though, that admission combined with several pieces of CCTV footage convinced him Halliwell was the killer.Suicide fear
Initial footage from Suju nightclub, where Sian had been, showed her getting into a car but the quality was not good enough to identify it.
"The key was finding another piece of CCTV from HSBC which gave us just a tiny corner of a police vehicle which was passing that point," Det Supt Fulcher said.
"That vehicle was a traffic vehicle that had ANPR on-board and that was able to give me a specific read of a green Toyota Avensis which was owned and driven by Christopher Halliwell."
As a result, they decided to follow the taxi driver and place him under round-the-clock surveillance rather than immediately arrest him, in the hope he would lead them to Sian.
The first night of surveillance was the "most worrying" as Fulcher was concerned Halliwell might take his own life because what he had done was weighing heavy on his mind.
"He was potentially going to commit suicide and therefore I would lose the last opportunity I felt I had to find Sian," he said.
Det Supt Fulcher admitted that if Halliwell had killed himself in his home on Ashbury Avenue "it would have ended my career, I'm sure".
Halliwell's eventual arrest came at an Asda supermarket on the outskirts of the Wiltshire town.
The killer had gone into the store and bought "a quantity of pills" and Det Supt Fulcher ordered his officers to swoop.
Halliwell's green Toyota Avensis taxi, with posters appealing for help to find Sian pinned in the back, was taken away.
Once Halliwell was in custody, Det Supt Fulcher made a decision that would help him find Miss O'Callaghan's body, but also ultimately lead to the defendant avoiding trial for Ms Godden's murder, when his methods were deemed unlawful by the court.
That decision involved taking Halliwell to a beauty spot at Barbury Castle near Savernake Forest, where the detective "appealed to the killer's conscience" over Sian.
"I asked him a number of times to do the right thing and I was able, over the course of that conversation, to persuade him to take me to where Sian was," he said.
Halliwell confessed he had moved Sian's body, before the police had started following him, to a remote spot, close to Uffington in Oxfordshire.
"Without his disclosure of Sian's location I don't believe there's very much likelihood of anybody finding her," Mr Fulcher said.'Momentary bond'
But Halliwell also admitted how he had killed Sian - by stabbing her in the back of the head.
"It was a very tense moment. It was a moment where success or failure hung on the relationship - at that moment in time - between myself and Halliwell," said Det Supt Fulcher.
"Any intervention at that time could have broken that momentary bond and he could have changed his mind and taken another course of action."
Halliwell's admission continued.
"He and I had another conversation together where he indicated that there was another body," said Det Supt Fulcher.
Halliwell said he could not be precise about the date the body of Miss Godden's had been buried, saying it was sometime between 2003 and 2005.
However, he was able to take police to the exact spot where she was buried, at Eastleach in Gloucestershire - some 15 miles from where Sian was found.
"He took me to a field at a crossroads," said Det Supt Fulcher. "We were able to cross the wall of the field and he was able to pace out an exact spot where he said he had buried a young girl."
A dig by police in the remote field led to the second body being found.No solicitor
But in the months that followed, legal argument would see the charges against Halliwell on suspicion of murdering Miss Godden dropped.
The media were not allowed to report the hearings until now.
Mrs Justice Cox ruled Det Supt Fulcher's actions as unlawful, as they had left Halliwell unable to see a solicitor immediately upon his arrest.
It meant that all of Det Supt Fulcher's evidence from the point he was arrested until he was taken to a police station was ruled as inadmissible.
The court later ordered that charges against Halliwell in connection with the killing of Miss Godden should lie on file.