The Investigator: A British Crime Story ITV, Thursday, 9pm

Williams-Thomas, the award-winning former police detective who unmasked Jimmy Savile as the UK’s most notorious paedophile, re-examines a previously ‘closed’ and chilling murder case, which has baffled detectives for more than 30 years.

The murder of Carole Packman, whose body has never been found, continues to affect the lives of many of those involved and as Williams-Thomas discovers, the shocking tale of murder, fraud, deceit and lies has left family members desperate for answers.

In a UK television first, The Investigator: A British Crime Story, will follow the case over four explosive episodes, combining stylized drama with compelling documentary.

In June 1985 the wife and mother mysteriously disappeared and has never been seen since. Her husband Russell Causley is now serving a life sentence for her murder, yet no body has ever been found. Throughout the case he pleaded his innocence and refused to talk.

During his investigation, Mark sets out to piece together evidence in a bid to find the truth. We grabbed Mark for a quick chat

What is your role in this new series?

“This time, I’m combining three roles - investigator, reporter and presenter. That means I’m able to explain and unpick threads of evidence as they unfold for viewers, interview protagonists face-to-face, and make the narrative of the story clear. Hopefully that makes for an engaging programme which people are drawn into following.”

Why pick this case to investigate?

“My profile since the Jimmy Savile programme has meant I am approached by people from all over the world to help investigate cases. “Some have been unsolved, some have resulted in conviction, and they involve a variety of things - missing people, sexual offences, possible miscarriages of justice, even murders.

“Yet the reason for every contact is the same - those people want to find out the truth. “In this case, I was contacted by Sam Gillingham to help find the answers to the many questions she still had about her mum’s disappearance over 30 years ago.

“Her dad was in jail for her murder, but he never gave evidence and remained silent and she had no idea where her mum was - she had never known the truth. That’s what first got my interest. This crime has taken over her life, become an obsession, almost - and yet the lack of a body, along with other elements of the story which have never been pieced together, has meant some questions remain unanswered. And that’s what I’m trying to do in this series.”

How did you approach the investigation?

“I approach every investigation in the same way - firstly I need to quickly establish that the enquiry is genuine and if my experience and skills can add anything to what has not already been done.

“Sometimes people are just looking for significant public attention and profile for their case, which could in itself be enough - particularly in cases where people are missing.

“One thing I always say to everyone whose case I take on is that they have to be prepared for whatever I dig up, good or bad. In this case, there are twists and turns throughout - I speak to everyone I possibly can, and go back into the trace evidence. That is no easy task when investigating a 30-year-old murder.”

What was the most eye-opening aspect of the case that you uncovered?

“I have investigated many murders and they all have some strange aspects to them when you start digging.

“But I have never investigated a case that has so many twists and turns like this one. At times it’s hard to believe it’s a real case and not something out of an Agatha Christie novel. Also sometimes what I set out to prove and establish at the beginning sometimes gets overtaken by other factors outside the case, and this was certainly the case here. I think that as the evidence unfolds, viewers will find it as shocking and compelling as I did.”

The Investigator: A British Crime Story ITV, Thursday, 9pm