ITV’s primetime drama about the investigation into the disappearance of Sian O’Callaghan continues tonight.

A Confession reaches its halfway point at 9pm as the net closes in on Christopher Halliwell, played by Joe Absolom.

Steve Fulcher, played by Martin Freeman, went against the advice of his superiors in 2011 and decided to take the taxi driver to a remote location and quiz him about the missing 22-year-old.

Sian had been missing for five days when police swooped on Halliwell.

Fulcher’s unorthodox decision had serious consequences for Fulcher and for the investigation as a whole – and led to an unexpected confession which gives the drama its title.

The second episode last Monday ended with Fulcher asking Halliwell “Are you going to tell me where she is?”

Tonight’s instalment will dramatise what was said between the pair during a four-hour conversation that provided a link to a previous case involving another missing woman, 20-year-old Becky Godden-Edwards.

Becky’s mum Karen told the Adver she believes there are more victims, possibly up to 20.