For more than three years, TV documentary cameras have recorded the gritty reality and daily dramas at Luton Police Station in Bedfordshire.

Murder, robbery and domestic abuse cases have all come under the microscope, with neither the filmmakers nor the investigating officers ever quite sure where each storyline will end.

None, certainly, were prepared for the twist that awaited when a man came into the station to make a complaint of blackmail: within hours, it became apparent that the prime suspect was one of their own detectives.

In tense scenes worthy of the police corruption drama Line Of Duty, the cameras capture the unfolding story as officers battle their feelings of disbelief and disgust as they bring one of their own to justice.

THE VICTIM

On a chilly weekday morning in March, a middle-aged man enters Luton Police Station clutching an envelope he has found on the windscreen of his car parked outside his house that morning.

Inside are pictures of him walking from a motorhome where, a week earlier, he had visited a prostitute in the Luton area. They are accompanied by a typed blackmail note.

In it, the writer — who signs himself ‘Light Justice’ demands £1,000 in return for his silence. ‘You have made an error in judgment. A massive error in judgment,’ it reads.

‘The next step is for you to decide. Do you really want the people closest to you to know about this? You made a bad decision and put your perversions above your family. You WILL pay £1,000 today.’

Instructions are given for a drop-off point for the money in a lay-by by 1pm that day.

The serious nature of the offence means that the Major Crime Unit, headed by Detective Chief Inspector Jerry Waite, are brought in to oversee the investigation. ‘Blackmail isn’t very common,’ he told the Mail.

‘We maybe get a report of one offence a year in Bedfordshire. A demand can start out as £1,000 — next week it could be £5,000, £10,000. Is it going to be a threat to their family? A wrong decision could totally affect someone’s life.’

While police don’t pay blackmail money, DS Will Taylor of Luton CID reveals that the victim — whose identity is disguised — is willing to use his own funds to plant at the drop-off point as a possible way of ensnaring the suspect. After the money is placed there in a used carrier bag, as requested in the note, a specialist police surveillance team monitor it from a hidden location.

THE INVESTIGATION

At the beginning of the investigation, detectives initially turned their attention to the prostitute who met the victim. She is known as 'Kirie'

THE police initially, turn their attention to the prostitute, a woman known as ‘Kirie’ who advertises her services on an adult-only website. ‘One of our first lines of inquiry was whether it was a set-up,’ says DCI Waite. ‘That was uppermost in my mind, along with the question of how the blackmailer had known how to contact the victim.’

A Major Crime Unit sergeant tracks Kirie down in Rotherham and brings her in for questioning, during which she maintains that she has nothing to hide.

‘I pay my taxes, I’ve got an accountant, I do everything above board. I am a limited company,’ she says.

Her claims are quickly backed and the police are satisfied she has nothing to do with the blackmail. However, four hours after the blackmailer’s 1pm deadline has passed there has been no suspicious activity at the drop-off area.

With Kirie out the picture, DCI Waite asks his team to see if anyone has performed any traceable online searches on the victim.

It emerges that someone has done precisely that: the victim’s car registration was looked up on the police national computer database several days before the blackmail was reported. The person who conducted the search? A CID detective from Bedfordshire Police’s Serious Organised Crime Unit by the name of Gareth Suffling.

The investigation quickly established a prime suspect - one of the force's own officers. DC Gareth Suffling had made incriminating searches on the police computer

More shocking still, he is on the surveillance team monitoring the drop-off area for the cash — meaning he is policing his own crime.

‘I was genuinely shocked,’ says DCI Waite. ‘I have had the displeasure of investigating police officers before, but this took me by surprise.’

Under the circumstances, the investigation now has to be kept as contained as possible: DCI Waite pulls a select few colleagues into a private room, where he tells them that a colleague is now the main suspect: ‘This doesn’t leave the room,’ he says.

‘When you’re investigating a police officer, you have to keep that investigation quite tight and within your investigation team,’ says DCI Waite.

‘There could be other officers involved; there could be other people outside the police service involved. You always have to ask yourself: “Could they be part of this?” The picture can change very quickly.’

THE SUSPECT

DC Suffling is married and a respected officer. His colleagues were shocked he was a suspect in the blackmail case

Everyone who met DC Gareth Suffling, a 35-year-old married officer, thought he was a fine detective — an ‘all round good egg’ in the words of his senior officer, DS Tom Hamm.

Weeks before the blackmail attempt, he had received a commendation for his investigation into a child sex abuser who groomed and sexually assaulted six teenage boys.

He had featured on a previous episode of 24 Hours In Police Custody, calmly interviewing another blackmail suspect.

‘Gareth was held in such high esteem. No one had a bad word to say about him,’ says DS Hamm. ‘He was really good at what he chose to do. He had the knowledge and he had the leadership — he could have gone as high as he wanted.’

As word gets round that Suffling is under suspicion, the sense of shock at Luton CID is palpable.

‘When you learn that someone who you’ve worked with for many months, someone you’ve admired because they’ve done a good job — I couldn’t believe it, it didn’t seem real,’ DS Hamm recalls.

‘You could have picked anybody and he would have been last on the list,’ adds DS Taylor, who worked with him. ‘And for what? A thousand pounds.’

For Waite, the sum is significant. ‘My personal feeling is it was an amount that was large enough to make it worth doing without being so large someone couldn’t pay it. I think that’s the amount he thought he could best get away with.’

THE ARREST

DC Suffling - wearing a grey T-shirt and jeans - is still on duty in the surveillance station when a colleague comes to arrest him

DC Gareth Suffling — clad in a grey T-shirt and jeans — is still at his surveillance station screen when the Major Crime Unit’s DS Mark Devine comes to arrest him.

Only two days earlier Devine has sat just a couple of seats away from Suffling at an internal conference.

‘He seemed a quiet unassuming kind of character,’ he recalls now.

‘You probably know I’ve met you before,’ he tells Suffling as he puts him in handcuffs and reads him his rights.

For Devine it was just another day’s work. ‘I didn’t treat him any differently than any other person I would arrest,’ he insists. ‘I view it as dealing with someone suspected of a criminal offence.

‘That said, I made the arrest so my colleagues didn’t have to in case they felt uncomfortable.’

Devine does his best to put Suffling at his ease, gently telling him his wife will know what’s happening because their house will be searched.

Following his arrest, DC Suffling, pictured here with his head in his hands, was visibly emotional. One officer said he was 'totally broken and sobbing’

‘I understand this is going to be upsetting,’ he adds. ‘Don’t think we’re getting any pleasure out of this.’ On the programme Suffling is clearly distressed, but DS Devine recalls that his demeanour was much more dramatic. ‘He was totally broken and sobbing.’

Suffling is taken to a police station in Cambridgeshire, away from his home turf,

‘It’s standard practice when you arrest a police officer,’ says DCI Waite. ‘Gossip can be an awkward thing and you don’t want to do anything that may hamper the investigation. It’s better for them to be away.’

The 24-hour custody clock starts to tick when Suffling is escorted to a cell, although not before he has made an emotional phone call to his wife.

‘I can’t talk about what’s gone on. I just wanted to say I love you and I’m sorry for everything and for any embarrassment that’s been caused,’ he tells her.

THE EVIDENCE

DCI Jerry Waite led the case. The story will be told in Channel 4 documentary 24 hours In Police Custody: Sex And Corruption

A team is sent to search Suffling’s house, briefed that it belongs to a fellow officer.

‘I do appreciate it’s not nice when you’ve got to do a search on one of your own, but at the end of the day you’ve got to do your job,’ DCI Waite tells them. They also need to be extra diligent: the suspect knows how the law works.

‘If you’re working on a case where the suspect is a police officer, you can’t forget that they know the criminal justice system as well, so there is an extreme amount of pressure to get it right,’ DCI Waite tells the Mail.

Suffling has done little to cover his tracks: in the kitchen bin is a torn up draft of the blackmail letter, as well as copies of the photos he had sent with the letter. Further paperwork sheds some light on a possible motive: a letter from Barclays Bank showed he was on a payment plan to pay off a £6,000 loan, of which £1,500 is outstanding.

Other paperwork shows Suffling, apparently unhappy as a detective, had been making inquiries about how to set himself up as a private investigator.

Meanwhile, CCTV footage of the car park where Kirie was plying her trade reveals a clear image of Suffling walking past the gates, having lain in wait for someone he believed was a suitable victim.

‘He’s woefully unaware of anti-surveillance techniques,’ an officer remarks, off-camera.

DCI Waite has another explanation. ‘I just think he got a bit arrogant about it,’ he says.

Either way his rookie errors are baffling to his contemporaries.

‘The fact is that Gareth was a very dedicated, competent detective and for him to think that he could get away with it — I just don’t understand,’ says DS Hamm.

‘The schoolboy errors he seems to have made just make me wonder what his frame of mind was at the time. Why was he so desperate to do what he did?’

It’s a question echoed by DCI Waite. ‘It’s a bit of a puzzle why someone would risk their income, their pension, their whole life, their family for the sake of a thousand pounds.’

THE INTERVIEW

Suffling has been in custody overnight when he is interviewed by a female officer. In the presence of a solicitor, he replies ‘No comment’ to all questions and replies ‘No’ when asked if he has anything further to add.

With the custody clock about to hit 24 hours, DCI Waite makes the decision to release him on bail.

‘We had a good case to charge but we’ve got outstanding inquiries and we want to get it right,’ he says. Suffling is also suspended from his duties as a police officer.

THE TWIST

Suffling had used his phone for some unpleasant business, too, using explicit search terms to access pornographic websites

A week after Suffling is bailed, DS Devine receives an email from his lawyer saying that his client has written a confession.

In it, he emphasises that he acted alone and did not plan to make any personal gain from the blackmail, but intended to help a vulnerable prostitute get on a drug referral scheme — schemes, he claims, he had researched on his phone.

His confession only incriminates him further: when officers from the Specialist Intelligence Unit analyse data downloaded from Suffling’s phone, it shows no such searches have been made. But he has made a Google search of the term ‘crime to make easy money’.

He had also visited the ‘Adultwork’ website and contacted Kirie to find out she was working from the motorhome near the industrial site in Luton where she had been visited by the victim.

Suffling had used his phone for some unpleasant business, too, using explicit search terms to access pornographic websites. He also made contact with four or five different massage parlours asking about their services.

‘He uses these sites for personal pleasure — he’s the equivalent of the guy he’s trying to blackmail,’ one unnamed officer points out.

JUSTICE AT LAST

Fall from grace: Suffling, pictured here at St Albans Crown Court, admitted charges of blackmail and misconduct in public office. He was sentenced to 18 months in prison

An emotional Suffling was charged with blackmail and misconduct in public office on May 24, when he answered bail.

Four months later, at St Albans Crown Court, he pleaded guilty to his offences, although he stuck to his story until the end, maintaining that all he wanted to do was help those in the sex industry.

The judge, Recorder Jeffrey Yearwood, didn’t believe him, saying he was ‘confident’ he could dismiss the explanation.

‘We always felt that the crime was motivated by financial gain,’ says DCI Waite today.

It’s a sentiment echoed by Bedfordshire Police’s chief constable, Jon Boutcher. ‘I think it came down to greed,’ he says.

Suffling was sentenced to 18 months — a sentence Boutcher felt did not sufficiently acknowledge the gravity of the offence.

He took the unusual decision of appealing to the High Court to ask for the sentence to be increased, and in November it was doubled to three years

‘I have nothing against DC Suffling,’ Boutcher said this week. ‘But we have a higher standard to display.

‘There is no protection of police officers who commit crime.’

Suffling remains in prison, his career in ruins. ‘There are some who would say that he was one of the force’s better officers, yet for some strange and inexplicable reason he chose to do what he did,’ says DCI Waite. ‘Now I just see him as a bent copper.’

- 24 hours In Police Custody: Sex And Corruption is on Channel 4 at 9pm tonight.