Andy Murray's journey from a tearful admission that his career was likely to end after a major hip surgery to winning an ATP title less than a year later is one of 2019's greatest sporting stories.

Now the British former world number one's emotional journey over the past two years has been laid bare in a behind-the-scenes documentary, Andy Murray: Resurfacing, which is being aired on Amazon Prime from Friday.

Here are eight things we've learned from it:

His childhood experiences in Dunblane led to anxiety

Murray, 32, grew up in the Scottish town of Dunblane and was a pupil of the local primary school when Thomas Hamilton killed 16 children and their teacher in March 1996. He hid in the headmaster's study when the tragedy happened.

Murray knew the gunman and opens up about the traumatic experiences of that day, along with other emotional family experiences which have shaped his life.

After previously being asked by director Olivia Cappuccini why tennis is important to him, the three-time Grand Slam champion finally responds in a powerful late-night voice message.

"Obviously I had the thing that happened at Dunblane, when I was around nine," he tells Cappuccini, who is the partner of Murray's brother-in-law, in December 2018.

"I am sure for all the kids there it would be difficult for different reasons. The fact we knew the guy, we went to his kids' club, he had been in our car, we had driven and dropped him off at train stations and things.

"And within 12 months of that, our parents got divorced. It is a difficult time for kids, to see that and not quite understand what is going on.

"And then six to 12 months after that, my brother Jamie also moved away from home. He went away to train to play tennis. We obviously used to do everything together. When he moved away that was also quite hard for me.

"Around that time and after that, for a year or so, I had lots of anxiety that came out when I was playing tennis. When I was competing I would get really bad breathing problems.

"Tennis is an escape for me in some ways because all of these things are bottled up and we don't talk about these things.

"Tennis allows me to be that child. That's why it is important to me."

The tears in Washington came because he thought his career was coming to an end

Following a first hip surgery in January 2018 and a tentative return later that year, Murray had the more serious resurfacing operation in January this year in a bid to rid himself of the chronic pain he was still suffering.

One of the most striking moments of the first comeback was the scene where, after he had beaten Romanian Marius Copil in the Washington Open third round at 3:02am local time, the Scot sat down in his chair, draped a towel over his head and sobbed uncontrollably for several minutes on court.

Now we are told the full extent of his mental state. That was the moment when he felt his career was coming to an end.

In a video message filmed at 5:09am in the American capital, he says: "I was really, really emotional at the end of the match because I feel this is the end for me.

"My body just doesn't want to do it any more and my mind doesn't want to push through the pain barrier any more.

"I was just hoping I was gonna feel better than this after 16, 17 months.

"It's just an emotional night because I felt I'm coming to an end. I'm really sad about that because I want to keep going but my body is telling me 'no'.

"It hurts and I'm sorry, I can't keep going."

Wife Kim told him to quit after 'bleak' Christmas phone call

After another tough training block in Miami towards the end of 2018, Murray said he was getting "zero enjoyment" from being on court.

He calls his wife Kim, who was back home in London, in a phone conversation which she describes as "pretty bleak".

"He always wanted someone to tell him to stop and I'd tried to explain nobody could because it was nobody's decision to make other than his," she says.

"I knew that is what he wanted and I knew what he was calling me for.

"I told him 'you're clearly not happy, you said you'd give it until Christmas - I was putting the Christmas tree up - call it a day'."

He almost changed his mind about emotional Australian Open announcement

Although Murray had privately been thinking he was approaching the end, he had given few clues publicly and that meant a tearful announcement in a pre-tournament news conference at the Australian Open surprised the world.

Murray said he thought he could get through the pain until Wimbledon and then stop playing, although he also conceded the Grand Slam in Melbourne might be his last tournament.

Yet on the morning of his planned admission he still had doubts whether he should reveal all.

"I'm going to say something today, I know I'll get emotional," he says, two hours before facing the media.

"But I change my mind all the time. I need to say something. Or I don't."

Murray describes how he is feeling nervous, anxious and has butterflies in his stomach, while walking around that morning without much pain in his hip.

"When making a decision like that I want my leg to feel really sore," he says.

That led to doubts. So he calls his physio Shane Annun. "I'm thinking I'm making a mistake," Murray says.

His surgeon warned him of the dangers of making a tennis comeback

Murray eventually chose to have the resurfacing operation with renowned surgeon Sarah Muirhead-Allwood, who had previously operated on the Queen Mother, at the London Hip Unit.

At a post-surgery meeting, Murray speaks of how he is worried about damaging his hip again and needing further surgery if he goes back to playing tennis.

"What if I said, if you went back to playing first-class tennis, I think you've got a 15% chance that in the first seven years you could destroy the hip," she tells him.

Murray laughs nervously.

"That is what it is like, it's not it will or it won't. It is chances. For seven years of tennis would you take that risk?"

Murray initially doubted whether he would return to the court because he said he was happy with being pain free and given a new lease of life.

But his mum Judy correctly predicts that will change.

"My gut is telling me he has unfinished business. He's not fooling me," she says.

He watched a gruesome video of the hip surgery

No holds are barred when it comes to seeing the footage from Murray's two hip surgeries.

Early in the film, we see graphic images of his operation with Australian surgeon John O'Donnell in January 2018 and Murray assessing his post-op scar which he concludes looks "pretty neat".

Later, after deciding in January this year he wanted to have the hip resurfaced, we see him watching a gory video of someone else having that operation.

"I find that funny, that they're literally using a hammer," he says.

Shortly after, he is having the operation for real. Everything from the moment he lies down on the surgical bed - including graphic images of bloody instruments working on the joint inside gaping flesh - is captured by the camera.

"It's not a good idea to be running around a tennis court," Murray says dryly as he comes around from the operation.

Wife Kim, along with fitness coach Matt Little and physio Annun, joke that the remark must be captured by the filmmaker because they know he will change his mind - again.

He has a bromance with his physio

Murray's 'bromance' with Annun provides the lighter, and funniest, moments of the film.

"I'd love to marry Shane, I'd have so much fun," says Murray.

Annun says Murray likes to tap into his weakness - being "gullible" - with his other physio Mark Bender saying he views the pair as an "old couple that know exactly what buttons to push".

The pair's relationship is again captured while they are starting Murray's rehabilitation work after the second hip operation, a warm and funny scene where Murray shows his affection for the physio.

"The brilliant thing about having a sore hip is I can hug Shane and he can't get away from me because otherwise he will hurt my hip. He can't force his way out of my hug," he laughs.

These exchanges show Murray's sharp sense of humour and how he like to "wind up" his team. Bender also bears the brunt of Murray's cheeky humour as we learn his nickname is 'Slender'.

"It's ironic because he's not particularly slender," giggles Murray.

He used to feel there was animosity towards him

Murray's announcement at the Australian Open that an illustrious career seemed to be heading towards the end brought a universal showing of affection and respect towards him.

But it has not been until recent years - following Wimbledon, Olympic and Davis Cup triumphs which endeared him further to the British public - that he has felt it.

"He did used to feel there was a certain amount of animosity towards him," his wife Kim says.

"I think he would accept now there is a lot of love out there. What he has done, I have to pinch myself sometimes. I can't believe I've watched it happen."