It was the work of a barely literate fantasist. So when a scrawled note turned up on his doormat, firefighter David Bryant could hardly have known it was be the start of a five-year living hell which would confine him to Dartmoor Prison, condemned as a paedophile.

It was only the tireless detective work of his wife Lynn that finally cleared his name against the vile, baseless allegations.

But just as Mr Bryant is beginning to pick up the pieces of a shattered life, tragedy has struck. The woman who supported him through the ordeal died two weeks ago from septicemia at the age of 54.

Support: Hero fireman David Bryant and wife Lynn at a Buckingham Palace garden party

He has little doubt that the unbearable strain of fighting the false allegations sent her to an early grave.

‘The whole thing took a huge toll on her and her health,’ says David, 66, a former station officer who received a commendation for risking his life in the 1987 hurricane.

‘If it hadn’t been for this case, I honestly think she’d still be with us. It may not have led directly to her death, but the years of fighting lowered her strength and her immune system. It was bound to take a toll.’

His faith in the police and the justice system have been badly shaken, and no wonder. Dorset Police was later criticised by an inquiry for being ‘misdirected by the policy of “believing victims”’, rather than properly investigating claims.

The Bryants’ world became truly Kafkaesque in October 2012, when a letter was dropped on their doormat from a man called Danny Day, claiming to have played darts with him in the fire station in ‘late ’76, early ’77’ and threatening: ‘I think it is time you and me had a chat. One way or another you will pay for what you done.’

The Bryants called the police to report a clear blackmail attempt, only to be told that Day had made ‘a serious allegation’ against David. Three days later, officers arrived at their £320,000 semi in Christchurch, Dorset, and seized the letter. Then the charge against him was revealed: Day had accused David and a late colleague of raping him on a pool table at the fire station when he was 13 or 14.

Fantasist: Danny Day falsely accused David and a late colleague of raping him on a pool table when he was 13 or 14

‘I said to Lynn, “Don’t worry, it’s a load of nonsense. The police will investigate it and that will be the end of it,” ’ recalls David. But it didn’t turn out that way as the flimsy claims were taken seriously. Hate mail and death threats followed. David was charged and convicted in December 2013. To make matters worse, David’s six-year sentence was later increased to eight-and-a-half by Appeal Court judges for being ‘unduly lenient’. Lynn, a water company customer services representative, collapsed in court at the verdict.

As David was taken to Dartmoor, Lynn turned sleuth, searching archives for anything to help her husband. ‘I couldn’t do much stuck inside,’ said David, ‘and she protected me from a lot – the strain on her was incredible.’

Through dogged determination, Lynn unearthed evidence proving that at the time of the alleged assault there was no pool table at the fire station and the layout was different from Day’s description.

The final straw came when Day launched a £100,000 civil claim. On top of everything else, Lynn faced homelessness. But although Day denies that his letter was blackmail, his greed would be his undoing. The Bryants’ legal team, working for free, were given Day’s medical records, which revealed that between 2000 and 2010 he told doctors he had a problem with ‘serial lying’, yet never once mentioned his ‘traumatic’ sexual assault.

It was to be the key to overturning David’s conviction and he walked free last summer.

He says: ‘We were looking forward to spending the rest of our lives together and to put all this horrible business behind us. Now I’ve got to face it alone without Lynn by my side.’

Their barrister Rupert Butler said: ‘Lynn was a woman of incredible faith. When David’s conviction was quashed it was down to her tenacity. She fought against formidable odds, and she won. I suspect that stress took a considerable toll on Lynn that finally broke her.

‘Hers and David’s is an extraordinary love story that deserved a happier ending than this.’

Dorset Police said: ‘Our thoughts are with Mrs Bryant’s family at this difficult time. Mr Bryant is liaising with our legal department and we are unable to comment further on these issues at this time.’