Bon Scott is an undisputed legend of Australian music but that may have never been the case but for a terrible motorbike crash.

Irene Thornton, his wife of two years and lifelong friend, has just released a tell-all book on their tumultuous time together, based on 15 never-before published letters by the rocker.

On the night of May 3, 1974, he sped off on in a drunken rage and was flung from his motorbike. He very nearly died, and spent almost a month in hospital, but Irene says after the accident 'his voice didn't sound the same'.

Bon Scott and Irene at a friend’s 21st birthday in the winter of 1974, after Bon’s bike accident

Bon Scott as his fans remember him, as the hard-rocking front-man for AC/DC. But for a boozy night which led to a horrific motorbike accident, it may never have been

Irene Thornton has based her story around 15 never-before-published love letters between the pair, focusing on their life together before the fame and fortune and her despair at his untimely death

Bon Scott was a free spirit rock and roller long before the heady days of AC/DC. He fronted middle-of-the-road bands in Adelaide, including one known as 'Fraternity'.

Even before fame and fortune beckoned, he partied long and hard. If a good time was to be had, the budding star was front and centre.

From awkward beginnings at the local drive-in, Bon and Irene would ultimately become an item.

Normally quietly spoken and reserved, Irene Thornton pulls no punches in the book.

'Bon was a risk-taker; it was just his nature,' she wrote.

'Whether it was booze or drugs or motorbikes, or anything else that took his fancy.'

But it's the revelation to Daily Mail Australia that a horrific crash in Adelaide's northern suburbs one drunken night changed everything.

Bon Scott lived hard and played hard. He died of acute alcoholic poisoning aged just 33

'Well I did feel that after he had the neck injury and broken collarbone and a cut in his throat, his voice didn’t sound the same,' Irene revealed.

'He didn’t seem to be able to do the same thing - he was doing a lot of melodic singing before, had a beautiful tone in his voice but I don’t think that (tone) was the voice he ended up with or that what he had (before) was the AC/DC voice everyone knows.

'I don’t think there would be much place for a tuneful singer in heavy rock.'

The newlyweds' time in the UK would put an unbearable strain on their relationship, which ended soon after they returned to Australia

The recovery was long and painful but, ultimately, fruitful.

'It was like he perfectly fitted the band,' she said.

'They were on the same level musically and once Bon had settled down into that band and found an image instead of, it looked like he was scrambling around for a look at the start with satin overalls on, I think they just suited each other.

'Bon’s personality was over the moon once he had found his niche.

AC/DC flirted with the idea of disbanding after the death of Bon Scott but his family was behind a push to keep going and so they did, going on to even greater success, with Brian Johnson leading the way

'But I do find it really puzzling that he just got bigger and bigger.

'That’s the sad part, he never knew. I just wish he could have known the heights he was going to achieve, it’s very sad.'

For Irene Thornton, turning the personal letters into a written account for public consumption, after all these years, was confronting for a mostly private person.

'I had moments where it was quite stressful having to throw in your past, which was something I wasn’t really comfortable about but it has to be all out there,' she said.

'I had been thinking about it for a long time and had a little collection of letters that I had written to my mother which had been given back to me when she passed away in the late 90s.

'I'd always kept little notes of what he said and would often tell little stories to people that amused them about Bon or things (I heard) that I knew weren’t right - a couple of friends along the way said don’t tell me, put in down in a book.

'So, I had quite a bit of that but I never really knew how to go about it, had the idea there all the time and when I sold my letters, it was that I just wanted all of them out there.

'I had to make it as continuous as it could be about the history Bon and I had and James Young who purchased the letters put the idea about a book (to me).

'He said he was able to make it happen and he did.'

Irene Thornton was just a teenager when they met, knew him well before fame and fortune went into over-drive and shared him on an intimate level, long before those four letters became household names.

AC/DC is still going strong 41 years later, despite the death of Bon Scott and the retirement of Malcolm Young

'I’d been with him during the tough and hard times and supported him financially and emotionally with helping with the band he was with at the time,' she said.

But his band's make-or-break trip to the UK, did just that. It broke them personally and him professionally.

'His original band (Fraternity) worked hard towards the goal to make it in London and it was a very hard time that we all went through,' Irene said.

'I think that’s why the friendship endured because he knew I had been there supporting them before he had achieved any sort of fame and success.

'We always had a good relationship, unfortunately it was really dampened by the circumstances we were in.'

Wedding bells. Irene Thornton says of her love for Bon Scott that 'I’m not one for corny things like that but I think I clicked more so with Bon than any other relationship before and certainly after'

And those circumstances 'broke the marriage up'.

'Bon wasn’t the same person when we came back and I was pretty jaded and fed up but he was pretty down once he realised things weren’t going to happen,' she added.

'The most important thing in Bon’s life was to be able to play music and to be in a band and after he put all his faith in Fraternity and that failed, it chipped away at us the whole time.

'There wasn’t so much of the lightness and laughter any more but after that there was still a deep caring on both sides about each other.

'After it was all over we were still able to laugh and talk and he wrote me lots of letters and confided in things when they were going well and when they weren’t going so well.'

On page 136 of 'My Bon Scott', Irene recalls how on one occasion 'the dark side of Bon'.

'I would never have imagined that he would do something like that but I remember that night very clearly and he was in one of his very dark moments,' she said.

'His face would just become very dark, his eyes would be dark and he would have this expression.

'He was very quiet that night and had a few sniggers and not many other comments in a room where there was a party atmosphere.

'He'd had been drinking a lot, that combination is not a very good combination when you’re feeling very down and a bit angry.'

'I sometimes wish I had married a bank clerk but I would have been bored out of my brains' says Irene Thornton

They had just returned from the unsuccessful trip to England.

'He must have been really festering about his hopeless situation.' she added.

'It was the only time ever that he was physical with me – he was so gentlemanly (usually) but I probably could have found some ways to diffuse things, probably in a party situation I would have dug my heels in and when I was pissed off with him I would let him know it.

'There’s always a way around it but that night I was adamant I wasn’t getting back on that bike.

'He picked me up and I shouted at him to put me down and he did and I landed with a bit of a thump and that was the only time, ever.'

Bon Scott wore the devil-may-care attitude proudly but Irene Thornton remembers a different man.

'There was that soft side, I wouldn’t have been able to entertain the idea of being with someone that was like the personality that you saw, it would have just been a hopeless situation,' she recalled.

'He did have a soft side and bit of an old fashioned side that came out.

'That’s the way that he was towards his family, a decent guy.

'He had an old-fashioned way of doing things - he wanted to ask my mum if he could marry me.

'Bon had an expression he used when we first were going out together that 'I’m from the old school’ and I sought of wondered what that school was sometimes … school of hard knocks maybe.

'He was very protective of me and not just me, anyone that was getting a rough deal Bon was always there to defend the other person or jump in physically to help.'

Her last memories of Bon Scott were that 'he was going to take us out to a Japanese restaurant' but he never made it because of a long day on the drink.

Irene was pregnant at the time to her partner Nick.

'I remember him (Bon) saying 'still love ya Rene'. He got in the car and went to the bottle shop to get more booze and he asked me if I was happy,' she said.

'I had another phone call when he left and he asked if everything was okay and if he could help financially.'

Bon Scott died on February 19, 1980, according to the coroner of acute alcohol poisoning. He was 33.

Even with revelations that guitarist Malcolm Young, 61, is now being cared for at a nursing home specialising in dementia treatment, Irene is adamant the show must go on.

'I think they (AC/DC) should go as long as they like if they are all happy because they had still been successfully even without Bon,' she said.

'If that’s what they want, they should because there are still millions of fans who want to see them regardless.'

Irene Thornton, will also forever be a conduit between two of the biggest names to front two of Australia's best-known music acts out of Adelaide.

Like AC/DC, Cold Chisel have their place in Australian music folklore and Irene, for her relationships with Bon Scott and then Ian Moss.

Bon Scott hams it up inside a photo booth camera. 'For me, being married to Bon Scott was a mixed blessing' says Irene

'Things like that I sort of was cringing at, as the details were dragged out of me, and I can only blame Vince Lovegrove,' she said.

Lovegrove was a singer with 'The Valentines' band, alongside Bon Scott, who he'd dragged across from The Spektors. He would go on to earn fame as a music writer and manager.

'Once I met him (Lovegrove) he introduced me to Bon and then Ian. Yes, Adelaide, that sleepy town, provided a couple of really good acts,' she added.

As for the question of whether the hardest of hard rockers was the love of her life, Irene Thornton remains non-committal 'I’m not one for corny things like that but I think I clicked more so with Bon than any other relationship before and certainly after'.

'I think they (AC/DC) should go as long as they like if they are all happy because they had still been successfully even without Bon' says Irene Thornton

'Our humour was the same, our background was the same right back to our education, the things that amused us. We were really on the same level.

Irene refers to her time as Bon Scott's wife in the book like this. 'For me, being married to Bon Scott was a mixed blessing'.