MILLIONS watched the moment a Wiltshire Police detective superintendent confronted killer Christopher Halliwell about the disappearance of a missing Swindon woman.

The second episode of primetime ITV drama A Confession ended with Det Supt Steve Fulcher making the decision to breach police procedure that would later cost him his career.

READ MORE: 'We don't speak like that'... Swindonians react to second episode

Mr Fulcher, played by Martin Freeman, took Halliwell to Barbury Castle for an urgent interview instead of cautioning him and reminding him of his right to remain silent.

He asked Halliwell point-blank about Sian O’Callaghan: “Are you going to tell me where she is?”. The pair came face to face during the fifth day of the investigation into the sudden disappearance of the 22-year-old.

Before heading to the Wiltshire countryside, Mr Fulcher went against the advice of his colleagues and decided not to bring the prime suspect straight to Gablecross Police Station for questioning following his arrest.

“We can’t let him hide behind ‘no comment’,” he told them.

“I’ve got nothing to lose, the minute he gets here with a solicitor, Sian’s dead.”

Before that, viewers across the country saw how the taxi driver first came under police suspicion.

Emotional scenes set nine years beforehand featured Halliwell murder victim Becky Godden-Edwards in the throes of addiction and her mum Karen, played by Imelda Staunton, trying unsuccessfully to keep her off drugs.

Mr Fulcher begins the hour wondering whether his colleague Ray Hayward, a fictional version of deputy chief constable David Ainsworth, could be involved somehow after he was found hanged at his home while facing misconduct allegations.

A breakthrough in the case came from a traffic officer using CCTV to spot the driver of the car Sian got during her night out at Suju nightclub in Old Town.

This led to Halliwell, played by Joe Absolom, becoming the chief suspect.

The net closed in on Halliwell as officers saw CCTV of him unable to look at a missing poster in a petrol station, visited his home to get a DNA sample and went undercover as taxi passengers.

Rather than swoop on the suspect straight away, Mr Fulcher put him under surveillance to see if Halliwell would lead them to Sian, but officers lost him on winding country roads.

A fake press release sent to the media in the hope of spooking Halliwell into breaking from his daily routine appeared to have worked.

Officers arrested Halliwell at 11.05am on March 24, 2011 on suspicion of kidnap, outside Asda Walmart at the Orbital, then at the same time cordoned off his house in Ashbury Avenue, Nythe. He had just bought a large amount of painkillers.

The time Mr Fulcher spent with Halliwell and the killer’s titular confession to killing Sian and Becky will be dramatised in next week’s episode, the mid-point of the six-part series.

Becky’s mum Karen told the Adver yesterday she fears there could be as many as 20 more victims of the Swindon killer.