THE mother of Sian O’Callaghan has been left ‘overwhelmed’ by the support shown from overseas after a documentary recounting the 22-year-old’s murder was aired in the USA.

See No Evil: Watch Me Disappear, on the Investigation Discovery channel, revealed CCTV and Automatic Numberplate Recognition (ANPR) was the key in apprehending double-murderer Christopher Halliwell.

Sian disappeared after a night out with friends at the Suju nightclub in Swindon in March 2011.

The documentary revealed suspicion swiftly fell on taxi driver Halliwell after his car was seen on CCTV repeatedly circling the area and pulling up beside Sian in High Street at 2.57am.

A flash of light then obscured the footage and when the car pulled away, Sian had vanished.

In what would turn out to be a fundamental break in the case, CCTV showed a police car by chance driving past the car.

The police car had an ANPR camera, the records of which Wiltshire Police used to identify Halliwell’s green Toyota Avensis.

Since the programme aired Sian’s mother Elaine Pickford, who appeared on the documentary, has been inundated with messages of support from American viewers, including one which said ‘Sian will never be forgotten’.

She said:“It is not easy considering and doing programs relating to Sian, they will go out no matter what and therefore I want Sian portrayed as she was, a truly special person and any account of matters relating to myself and the family to be relayed the best I can.

“The support from both people who had the pleasure of knowing Sian and those from far and wide continues and is comforting and great testament to Sian.”

The US documentary used actors to play Sian, Sian’s boyfriend Kevin Reape, her mother Elaine Pickford, Christopher Halliwell and lead officer Steve Fulcher.

It showed harrowing CCTV footage of Halliwell coming face to face with one of Sian’s missing person’s posters in a petrol station along with video of Sian making her way out of Suju.

Elaine said the documentary had thrown up some painful memories as it included reconstructions of Sian’s murder.

She said: “I was not expecting the use of actors for myself, some family members and Kevin, the reconstruction of Sian’s murder in the car was difficult and of course it’s not known exactly how or where it took place. It was very upsetting and difficult to watch.”

“At least myself, Sean Memory and Mandy Stevenson gave the true account of what was going on rather than have the program go out without that.”

Halliwell would ultimately lead police to Sian’s body near the Uffington White Horse and to the remains of Becky Godden in Eastleach, Gloucestershire.

Elaine said: “It means a lot the programme and Sian have been well received and may help with awareness.

“Sian will always be remembered because her personality was so big and so loveable and because she was so popular, so vibrant, so happy.”