At the same time, she was compelled by music. As precocious 10-year-olds, Winehouse and Ashby styled themselves as a Salt-N-Pepa-inspired hip hop duo, Sweet ‘N’ Sour (with Amy casting herself as the latter). Winehouse’s first studio experience came when, impressed, Ashby’s stepfather Alan Glass, a US producer and composer who’d written for Aretha Franklin and Al Green, offered to record the pair’s efforts.

“To be honest, for two north London 10-year-old girls we had some serious skills,” says Ashby. “The American accent down and clever lyrics. We were just two hyperactive kids. We couldn’t wait to get on the mic. It was such a special time for us…definitely something that shaped us as kids.”

After hip hop, Winehouse was turned onto jazz by her part-time pub crooner father. “My dad liked Sarah Vaughan, a lot of Sinatra, Tony Bennett,” she told this writer in 2007. “Then when I was about 13 or 14 my brother [Alex, three years older] was listening to a lot of jazz. I guess I learnt to sing with soloists. Sax solos and stuff like that.”

Naturally rebellious, she didn’t fare well at Ashmole secondary school in Southgate, leading to a fateful argument with the deputy head teacher. “I was just trying to wind him up,” Amy remembered. “I went [cartoon sneer], ‘I’m gonna go to stage school.’ And he goes, ‘Amy, stage school is a fantasy…it’s not what people really do.’”

But in her case, her talent already radiating, Winehouse managed to secure a scholarship to attend the Sylvia Young Theatre School from the age of 13. Although confrontationally mouthy, in truth Amy was always self-doubting. “What I learnt at Sylvia Young’s,” she confessed, “was how to put yourself forward for things and think, Yeah, I am good and I can do this.”

At 16, she enrolled on the musical theatre course at The BRIT School in Croydon, but quickly grew disenchanted. “I walked out,” she said. “I just thought, Fuck this. I admittedly did the wrong course. I should have done music.” Instead, she began attending Saturday morning National Youth Jazz Orchestra sessions at The Cockpit Theatre in Marylebone, where she was given the chance to sing with a big band.

“She was this moody, chubby, Jewish-looking teenager,” says Annabel Williams, her singing coach with the NYJO. “She seemed fairly quiet and uninterested. Amy first stood out to me when she was in the centre of all the musicians and started singing. I was just like, Woah, she’s amazing. She absolutely nailed it and I was so impressed.”
From here, Winehouse began performing backroom pub sets, facing a crowd with just her voice and acoustic guitar. At the same time, she began guesting with a loose north London collective called The Bolsha Band, through which she met her long-term live keyboard-player Sam Beste.

“She said to me, ‘Do you like Thelonius Monk?’” Beste recalls. “People like Dinah Washington and Ray Charles and Donny Hathaway, she really connected with those musicians on a very deep, emotional, raw level. There was a strange awkwardness about Amy. Even in those early days when we were playing the small clubs, she wasn’t really engaging with an audience in the way that an entertainer would. She was a bit in her own world.”

Through a singer friend, Tyler James, 16-year-old Amy came to the attention of Nick Shymansky, then a teenage scout at Simon Fuller’s 19 management company, who had designs on matching James with a female singer to create a Marvin Gaye/Tammi Terrell-styled soul duo. Shymansky chased and chased a reluctant Winehouse and finally managed to pin her down. “She wasn’t very nice on the phone,” he remembers, though warmly. “She was kinda like, ‘Who the fuck are you? Why would I wanna meet up with you?’ I think her initial reaction was fear.”

In time, Amy sent Shymansky a jiffy bag adorned with “probably five hundred childish stickers of hearts” and containing a cassette, which the aspiring manager first played while driving. “It was a cover of Night And Day,” he says. “I had to pull over. I remember just thinking, Holy shit. I knew I’d found something really special.”

Winehouse was coy about her own songwriting, but showed Shymansky some poems she’d penned, which yielded still-unheard early compositions such as Estrogenius and the impishly-titled Monkey Not A Boy. Still, Amy seemed deeply unsure when it came to her gifts.

“She was very complex,” Shymansky reasons. “A lot of the things that the average person would think were brilliant about her were second nature and therefore unimpressive to her. She didn’t rate herself. Her songs were really dark, really sad, really self-critical.”

In early 2002, the 18-year-old Amy Winehouse, accompanied by Nick Shymansky, flew to the States for the first time, landing in Miami. Though it had proved tough for the manager to stir up record company interest in the singer, EMI Music Publishing had funded this trip to Florida for Winehouse to write and record with Fugees/Nas producer Salaam Remi. It was a thrilling time for the pair: riding around in a rented convertible, staying at the art deco Raleigh Hotel on the city’s South Beach.

“Salaam just got it from the off,” says Shymansky. “He and Amy were jazz and hip hop nuts. One minute they’d jump on the keys, next minute guitar, next minute double bass. Salaam was always a much better player than Amy but he’s not a player and Amy wasn’t a player. It dropped Amy’s insecurity that you have to be the most accomplished musician to be respected by other musicians.”

Moreover, without attempting to lighten the darkness in Winehouse’s songs, Remi encouraged the young singer to enhance the twisted humour in her writing. “What I allowed her to do was really just put wit into her songs,” he says in Amy.

In this environment, Winehouse flourished as an unflinchingly candid and luridly caustic songwriter. “Everything about Amy was like one big diary,” says Shymansky. “She would be spilling out her views. Sometimes her views were really raw and emotional and sometimes they’d be really funny and piss-taking.”

Aside from humour or personal confession, Winehouse pointed the finger at others in the songs which would feature on Frank. On Stronger Than Me, she taunted her then-boyfriend Chris Taylor, seven years her senior, for what she perceived as his lack of emotional strength (“Are you gay?” she baitingly wondered). In What Is It About Men, she publicly opened a can of worms, by addressing her parents’ separation when she was nine; Mitch leaving Janis after a long-term affair with a work colleague.

“I tend to write songs about things that I can’t quite get past,” Amy told me. “I wasn’t messed up about it. But it was something I was trying to make sense of. He’s been asked about it and he’s a bit like, ‘Well Amy’s Amy.’”

“I met my current wife and that was it,” Mitch Winehouse stressed when I asked him about the song in 2007. “I didn’t have a harem or anything. A lot of my friends find it difficult because we came from the moon in June and isn’t love lovely type of songs. She’s someone who sees it slightly differently.”

In the end, Amy wasn’t entirely satisfied with Frank. She moaned about how Island had forced her to include one song she hated, the Erykah Badu-lite of Amy Amy Amy, and claimed the label had “fake strings” overdubbed against her will on the downtempo soul reverie of Take The Box.

“She felt that spoiled the aesthetic of the record,” says then A&R manager, now president of Island, Darcus Beese. “No one should be happy with their first album. I always say, ‘How can you be happy with your first album when you’re still learning your trade?’”

“There was an element of tough love that had to happen to make the record,” Nick Shymansky points out. “I’m sure she would’ve made a record, ‘cause she was brilliant. But there was no structure. It may have taken 10 years.”

Where Winehouse maintained absolute control was on stage. Dale Davis played bass live with Amy from her second professional gig to her last and remembers being taken aback by their third together in Powis Square at the Notting Hill Carnival in August 2003. “Carnival crowds are never the easiest,” he states. “But her performance was so powerful. She didn’t need a band onstage, all she needed was herself and the guitar. Her singing was devastating.”

Davis remembers that Winehouse, truly soulful as a performer, never sang a song exactly the same twice, teasing fresh nuances from the material night after night. “After four or five shows of doing one song, she’d changed the song completely,” he says. “You could hear her working the changes every night. I think ultimately that cost her, because she gave so much in performance and in her personal life that she just left herself short. You get a lot of artists who sing the same every night and they preserve themselves as a result. But with someone like Amy, who gave her all every single night, that leads to a bit of burnout.”

Touring for Frank completed, in January 2005, Amy moved to Camden, at the time a post-Libertines hive of indie hedonism. Seemingly utterly uninterested in writing songs for her second album, she dossed around, smoked weed, got drunk and played pool for hours each day.

“She’d been busy for five years,” says Nick Shymansky, “All of a sudden she wasn’t busy. Expectations hadn’t been met. Money was tight because we took a loss on the touring. And she’d upset a lot of people.”

“I started playing pool all day because I could,” Amy remembered with a shrug. “The record company would come and see me playing pool in the pub and they’d be like, ‘Do you still want to make a record?’ I’m like, ‘Yeah, it’s coming, I’m just gonna play pool for three months, yeah?’”

On the Camden scene, in the summer of 2005, Winehouse first encountered the controversial figure of Blake Fielder-Civil, whose name she impulsively had tattooed onto her left breast. When Fielder-Civil ended their affair to return to his girlfriend at the end of that summer, Amy fell apart, drinking Jack Daniels from the moment she woke up, slumped in a sobbing heap on her kitchen floor. Though in a worrying state, the breakup was the grit which began to produce the songwriting pearls for Back To Black.

Winehouse’s friend and then-flatmate Juliette Ashby is in no doubt as to why that album was such a creative success. “Pain,” she says. “Pain can make you write like you’ve never written before. Being happy is wonderful but doesn’t get you the music that hits you in the stomach when you hear it.”

After 18 months of troubled downtime, according to Salaam Remi, Island were considering dropping Winehouse. “The label were considering letting her go,” the producer claims in Amy. “She ends up coming back to Miami. Guy Moot [EMI Music Publishing] calls me up. ‘Hey, you sure you wanna do this?’ I was like, ‘Listen, even if you dropped her, I will pay her to come to my house and sing, ‘cause this shit fucking moves me.’”

“If someone takes three years to write a follow-up,” says Darcus Beese from the perspective of the record company, “things are gonna be said and people are gonna have opinions. But I can’t ever remembering someone sitting me down and saying, ‘We’re gonna drop your act.’”

“She totally didn’t drink the whole time she was here,” Remi says of the Miami sessions for Back To Black. “She sat out in my back garden for four days. She’d take a little notebook and just keep writing.”

At the same time, Island also hooked Winehouse up with Mark Ronson in Manhattan. He remembers being warned by people in the industry that the collaboration would likely turn out to be an unproductive nightmare. “They were just like, [sarcastically] ‘Oh good luck’,” he says today. “‘I heard she’s been working on that record for three years.’”

But, in Miami and New York, Amy was suddenly energised and, working quickly and intensively, bottled lightning. “I was really inspired,” says Ronson, remembering their first day together in the studio. “Both by her and the kind of music she was talking about wanting to make, playing The Shangri-Las and stuff. When she left that night I wrote the music for [the song] Back To Black and played it for her the next morning. She was like, ‘That’s what I want my album to sound like.’ So she wrote Back To Black in, like, three hours.”

Meanwhile Rehab, set to become her comeback single, was written after a conversation with Ronson about her recent problems. It was transformed overnight by the producer from what he describes as “a sort of Johnny Cash Folsom Prison Blues kind of thing. She showed me the chords and went home. So I sped it up and did that ‘60s picking, strumming thing. She came back in the next day and said, ‘Yeah it’s cool, it sounds like The Libertines.’”

Ronson still marvels at the memory of watching Winehouse in the moments when she lost herself in songwriting. “The thunderbolt strikes the head, the pen scribbles furiously and that’s the song,” he says. “When she wrote, there was no editing. It came out, like, this is the truth and this is how it’s gonna stay. She never second-guessed that and that’s why those lyrics are from another place.”

Talking to Amy four months after the release of Back To Black, it was clear she knew the album was a triumph. “I made an album of 11 songs that I’m so proud of,” she beamed. “I was listening to a very narrow spectrum of music, so all of the stuff kind of sounds the same. Whereas the first album was a bit of a melting pot, really. When I gave it to the record company, I said, ‘Do whatever you want…first single, second single, third single.’”

Still, Winehouse was unprepared and ill-equipped for the almost inevitable success of Back To Black, which by the end of 2007 had gone six times platinum in the UK alone. With the return of Blake Fielder-Civil, and their marriage in May 2007, Amy’s life for the next year-and-a-half became a drug-disorientated, paparazzi-trolled horror show.

Even in February 2008, when briefly clean of illegal substances, but forced to perform her live segment for the Grammys from the Riverside Theatre in Hammersmith after failing a drug test for her US visa, Winehouse seemed unable to enjoy the fact that she’d astonishingly bagged five awards.

“I’m looking at her, trying to get some sort of reaction,” remembers Juliette Ashby of that night in Amy. “She went ‘Jules, this is so boring without drugs.’ And I felt really, really, really sad for her.”

In the midst of the chaos, Amy Winehouse struggled to come up with anything substantial for a third album. “She was writing in amongst all the madness that was going on,” says Island’s Darcus Beese. “You’re in a dilemma. You’re conflicted between do you get in a place where she’s creative and keeping her mind busy? Or do you let her just go away and disappear? I was of the mind that you needed to keep her busy.”

As a result, during 2009, Sam Beste was charged with the task of visiting Winehouse once a fortnight at her new home near Enfield, in an effort to just play together and hopefully inspire her musically. “She was sort of perpetually in this state of distraction,” Beste says of these failed sessions. “One time we did actually talk properly and she sort of broke down and started crying and saying that she knew that everything was falling apart and she wanted to sort herself out.”

In Winehouse’s attic studio, the pair would try to work through soul songs or selections from jazz sheet music bible The Real Book. Alarmingly quickly though, Amy’s mind would start to wander. “We’d get three bars into a Donny Hathaway song or something,” Beste recalls, “and she would say, ‘I’m bored.’ Then we’d move onto another song and do that three or four more times and then she’d leave the room. She was just really struggling. Physically and mentally really unwell. It was very hard to know what to do.”

The same year, Salaam Remi was flown over to work with Amy in the attic, resulting in sketches for two new songs, Between The Cheats and Like Smoke. In October 2010, when I was interviewing her at the Q Awards, Winehouse was tipsy but bright-eyed and claimed that the album was in fact progressing, naming two new songs, Gutter and Our Souls Ain’t Sold. “It’s going really well, thank you,” she insisted. “What’s the style like? I couldn’t tell you yet…”

One key moment in Amy reveals where her thoughts lay when it came to stylistically imagining her next record. In a voicemail to Salaam Remi, Winehouse is heard buzzing about her recent periods of properly absorbed writing. “I keep coming out with battle raps and they’re just pouring out of me,” she tells the producer. “Like Wu-Tang stuff, but really neat, very beautifully alliterated little battle raps. I’m fucked up in the head, but I keep coming out with all this stuff all the time, all these lyrics and…I don’t know why. But I realise it’s for the next album.”

If nothing else, this is evidence that Winehouse’s fighting spirit seemed to be returning to her. In tandem, she was also planning a jazz project with Mos Def, Raphael Saadiq and Questlove and would send the latter countless MP3s as reference points. “I thought I had my doctorate in jazz, but no, she taught me a lot,” Questlove stresses in Amy. “She, like, assigned homework. ‘Study this record, study this record, study this record.’”

While admitting that Winehouse’s vocal power had diminished as a result of her indulgences, Dale Davis can picture another direction in which Amy might have headed. “I could’ve seen her moving towards ‘70s soul,” he says. “She was a massive Minnie Riperton fan and I could’ve seen her going down that route. But the thing with Amy, ‘cause she had that talent, she could’ve gone anywhere really.”

At the very end, out of character, even Amy Winehouse herself seemed to have finally recognised and accepted her rare and precious talent. On Friday July 22, 2011, the night before Winehouse’s heart finally stopped beating, her bodyguard Andrew Morris remembers discovering her watching old footage of herself on YouTube. “She was showing me some clips on her laptop,” he painfully remembers in the final moments of Amy. “She said, ‘Boy, I can sing.’”