Frank Fulker, 72, pictured above left, regretted his infidelity - but 30 years later he was dragged through the courts on a false allegation of rape. Here he is pictured with his 69-year-old wife Jacque, above right

Frank Fulker was hardly the first married man to harbour a guilty secret.

He immediately regretted his infidelity – a fumbled encounter in the back of a car – and was mortified when, eventually, his wife found out.

But however shameful, it could hardly warrant what would happen a full 30 years later when two detectives walked up the path to his house.

That knock on the door was the beginning of a terrifying four-year ordeal that would shatter his life and that of his family, threaten him with a jail cell, and destroy for ever his faith in Britain’s system of criminal justice.

On the flimsiest and most inconsistent of evidence, Mr Fulker found himself accused of rape, only to be cleared unanimously after a court heard that the ‘victim’ was not only delusional shortly before contacting police, but had even handed Mr Fulker a condom before they had sex all those years ago.

But however clear the outcome was in court, piecing their lives back together is not so easy for Frank, 72, and his 69-year-old wife Jacque – pronounced Jackie.

Today, Frank is waiting for surgery for a leaking heart valve, a condition his doctors say has been worsened by the stress.

His days as a property developer in Sussex are over, but so too is the dream of a peaceful retirement.

He is furious at the treatment he and his wife have suffered, and scathing about the police’s insistence that the ‘victim’ must be believed, however flawed their story. It was, he says, a ‘journey through hell’.

Mr Fulker, a father-of-four and grandfather-of-ten, was inspired to come forward to tell his story after reading an article in this newspaper two weeks ago about the case of former fire officer David Bryant, who was jailed, then dramatically cleared on appeal, for a historic sex offence.

The two innocent men are among numerous suspects whose names have been dragged through the mud on spurious grounds as detectives work from the benchmark that people complaining of abuse ‘should be believed’ in the wake of the Jimmy Savile scandal.

Along with ordinary men like Mr Fulker and Mr Bryant, a host of celebrities and prominent people have faced similar exposure, including Sir Cliff Richard, Paul Gambaccini, the late Lord (Leon) Brittan, and war hero Field Marshal Lord Bramall.

For Mr Fulker, it all started in 1983 when Jacque was in hospital and was visited by her husband and a female married friend who, for legal reasons, must remain anonymous.

Mr Fulker recalled how, after the hospital visit, he gave the woman, whom we will call Jane, a lift home.

He said his passenger suddenly began telling him intimate details about her marital life. ‘As she was saying these things, she was giggling, then touching me on the leg, really coming on to me.

'I was going through a lot of stress with four children to look after and a wife in hospital. I know it’s no excuse, but like a fool I gave in to temptation.

Keeping a secret: Frank with Jacque at a dinner dance in the 1980s

‘We drove on to a dark lane and had consensual sex on the back seat. I had to unstrap the baby seat first and put it in the boot. She actually gave me a condom.

'The next morning I thought, oh my God, what have I done. She phoned me up and said she still had two condoms left, could we carry on? I said, look, we’re both married, I don’t want an affair.’

But they remained friends, with the two couples attending the same parties for the next three decades or so. There was no more sex, nor was it mentioned, and for Frank it became a distant, if guilty, secret.

By 2012, Jane was suffering from a psychiatric disorder and during her treatment told her husband and doctors about the 1983 episode with Mr Fulker.

Her husband’s first reaction was to call Jacque, who recalled: ‘He asked me round to his house. He couldn’t speak at first, but then he eventually cried, put his head on my shoulder and said, “They’ve… had sex.”

‘It was only when I was driving away that it hit me. I pulled into a lay-by and realised that the man I’d been with since a teenager – both of us virgins – had cheated on me with someone I knew. I was terribly hurt. I wanted to throw my wedding ring at him.’

Frank recalled: ‘When her husband asked to see Jacque on her own, I knew straight away. I thought, “Oh God.” ’

After anguished discussions with their grown-up children, Jacque decided to forgive him and move on. But Jane’s husband had other ideas and, according to the Fulkers, could not come to terms with the idea that his wife had willingly slept with another man.

In March 2013, the Fulkers were astonished when two detectives turned up at their door and told them that Jane’s husband had made a complaint of rape.

Frank told his story – and a log made by one of the detectives and disclosed during the trial concluded: ‘I am happy that there have not been any offences take place [sic].

'It is clear from both parties that this was a brief affair which has only come to light again due to [Jane’s] decline in mental health.’

Feeling confident that the accusation had been dealt with, the Fulkers put the matter out of their minds. But in May 2015, Frank received a call from another Sussex detective, asking him to come in ‘for a chat’.

Mr Fulker said: ‘I was given a duty solicitor and arrested, and the interview was taped under caution. I made a statement and I admitted I had sex with her and told them she was really keen on me and she was pushing it. ‘

Frank wasn’t charged until March 17, 2016. He said: ‘When I was charged I said, “Not guilty, I have never in my life been violent to any woman. Sussex Police are not fit for purpose.”

'They wouldn’t type the last bit on the form at first, but I insisted and they finally did.’

Inspiration: Our report about fireman David Bryant's similar ordeal. He was was jailed, then dramatically cleared on appeal, for a historic sex offence

He added: ‘I was so shocked, the officer offered to drive me home. He said I shouldn’t be driving.’

As the trial date approached, Frank hired a barrister, Elizabeth Nartey, but he and Jacque, with the help of their son and daughters, performed all the paperwork and legal correspondence that would normally fall to a solicitor.

As evidence began to be passed over by the prosecution under the discovery process, a troubling picture of Jane’s mental state became apparent.

In her statement, she claimed that Jacque told her that Frank had once had sex with an ‘aborigine woman’ on holiday in South Africa behind a bush.

In February 2013, she had telephoned an investigating officer after an interview telling him she’d recalled once being in a playhouse in the garden where ‘people were having sex with her’.

Most damning of all in the police log were details of a letter from Jane’s GP, and a note from a Detective Constable Parkinson who had written: ‘The letter states in capitals, “THERE IS ABSOLUTELY NO REFERENCE [in medical records] TO ANY EVENT WHICH COULD BE RELATED TO THIS REPORT OF ASSULT [sic].” ’

The detective’s log continued: ‘The letter also stated her M/H [mental health] issues is of a relatively recent onset. She had no M/H illness prior to 2012 when she initially reported vague symptoms such as difficulty distinguishing reality.

'However within a month she deteriorated rapidly, needing prolonged in-patient psychiatric treatment for a delusional disorder.’

It seems unsurprising then that, when the case came to Hove Crown Court in January, the judge gave the prosecution a chance to withdraw the case, asking if the Crown had properly reviewed this case in light of the evidence and Mr Fulker’s good character.

The prosecutor said it was the Crown’s intention to proceed on the basis that they could not say that the ‘complainant was not capable of being believed’.

Some of the exchanges in court would have bordered on the farcical if the stakes had not been so high. Mr Fulker said: ‘When I was cross-examined, it was put to me over and again that I must have had a black Range Rover as the complainant said in her statement. But I had a silver Rover 2.6 back then.’

The astonished jurors heard that during Mr Fulker’s police interview, DC Parkinson stated twice that the complainant had told police she had given Mr Fulker the condom – which matched his own account.

Under cross-examination, DC Parkinson said the suggestion that the complainant supplied the condom had been a ‘mistake’ on his part. In her taped statement, the woman claimed Mr Fulker supplied the condom.

After a week-long trial, the jury of six men and six women returned a unanimous Not Guilty verdict after just two hours’ deliberation.

Today Mr Fulker is considering legal action. He makes no secret of his feelings about DC Parkinson, saying: ‘I’d like to see him busted down to a traffic warden.’

He decries the College of Policing guidelines which insist that people reporting sexual assault must be believed to encourage more victims to come forward. The guidelines are being reviewed.

‘I’ve no objection at all to police taking victims seriously, but the allegations have to be tested and investigated properly, not simply taken at face value,’ he said.

For the woman and her husband who brought the allegations, he has only contempt. ‘I’d like them to have a taste of the four-and-a-half years of pain we’ve been through, then justice would be done.’

A Crown Prosecution Service spokesman said: ‘The role of the CPS is to assess if there is a realistic prospect of conviction and if it is in the public interest to prosecute.

'In this case, the judge agreed that the evidence was sufficient for the case to be left to the jury and we respect their decision.’

In a statement, the complainant, who is now in her 60s, and her husband said they were ‘disappointed’ with the outcome.

They refuted Mr Fulker’s claim that the reporting of the allegation was at her husband’s prompting due to his disbelief that consent was given.

The statement said: ‘Rape is an incredibly serious matter… and we are thankful that the case was pursued.’

A Sussex Police spokesman said: ‘Prosecution witnesses who gave evidence were open to challenge by the defence in cross-examination, and we have not been told of any criticism of the prosecution or police by the trial judge.’

He said a complaint by Mr Fulker about the detective in his case had ruled there was no misconduct.