Over a decade may have passed, trends have changed, and The X Factor fails to capture audiences like it used to, but it's still a memory that remains fresh in many of our minds.

The iconic win broke the first of many records for Lewis. Amongst others, she became the first female winner of The X Factor and boasts the best-selling debut album by a female artist in the UK in the 21st Century. Ten Brit and Grammy Award nominations, and over 30 million global album sales later, her portfolio features some incredible achievements. When we meet in her PR’s chic headquarters in Mayfair, Lewis laughs and shakes her head in disbelief reflecting on that iconic night.

“It's mad! In one breath it does feel like 15 years because I’ve done so much in that time, so much has happened and so much has changed, you know? But in another breath, it feels like yesterday. A lot of people would be surprised to hear it's been over a decade! When I'm back in the UK people still tell me that they voted for me on The X Factor, and it’s so crazy how it takes people back to that moment in time, and how vividly people remember that night.”

Since stepping out from the comfort of Syco, Lewis has tested major record labels and imprints, most recently dipping into the waters of independent music, and for the last five years she has navigated life on her own terms. With the space and time to experiment with new ventures, she admits it's been tough with a small team, but ultimately the decision has led to some unique opportunities, unearthing a love of acting, performing in Cats on Broadway, and even featuring in The Oath, a TV series produced by 50 Cent.

“I’ve done so many things that I never thought I would, that I probably wouldn't have had the time to do in a record deal. It's given me so much more time to explore a different side of myself.”

“Right now, I'm working with Sony on my Christmas album, and it’s amazing that I have a lot of support, which I need for a record like this. As far as new music goes it's been really fun and I hoped to release some music this year, but with everything that’s happened it's been pushed back. I'm still working on those songs now, so there'll be an EP or an album out in the next year or so", Lewis explains. "Since everything stopped, I didn't feel like I’m chasing anything or feel any sense of urgency, so there's really not much pressure, but all that pressure comes from myself. I just need to stay true to what I wanted to do, which was to bring these songs to fruition. I can be that person who starts a thousand things and never gets round to finishing them, so I took this time during lockdown to finish off a lot of ideas as well, like a TV show concept, and an independent film I’d love to shoot at some point too.”

Reflecting on her Nine Songs selections, both the choices and our conversation are full of nostalgic time capsules for Lewis - the soulful R&B vocals of 90’s girl bands, first-dance wedding grooves in Sting’s Tuscan mansion, an operatic education, and the tragic death of Lady Diana. The songs span the breadth of her musical career, from bursting out with love ballads as a tiny tot, to classic hits that have remained a constant throughout her life. Our discussion turns to longevity in talent shows, and I ask her about The X Factor’s downfall in recent years.

“I feel like with everything, you embrace it and then sometimes the audience craves something new. Or, the problem is you're trying to chase something that's already happened, but lightning doesn't strike twice. You’ve almost got to go away and re-think it, stop grasping onto something that's already happened and do something completely new, out-of-the-box fresh. It can be revitalised in a new way, but things run their course and nothing lasts forever - we don’t, nothing does.”

“When I first auditioned there was more of a focus on people who seriously wanted to be recording artists, because the prize was a record deal. But I feel like people always crave talent shows, especially programmes like The X Factor, where you also get to know the person and a bit of their story. You really humanise the person. It exposes that we're all normal people, and yes, some of our situations are very different, but we're all going through different challenges and obstacles.”

If we could somehow zip back in some wonky time machine, there are so many achievements the singer/songwriter might want to revisit in her career. Maybe a trip to witness one of her many broken records, perhaps the release of debut album Spirit, or even one of her quieter moments? But ahead of her 15-year X Factor milestone, we revisit her mindset at the time. Of course it's no easy feat being thrown into stardom at any age, let alone in the minefield of your early-20s. Amongst the chaotic kaleidoscopic blur of lights, cameras, and being broadcast to millions of people across the country, she tells me it was all too easy to get wrapped up in the negatives.

I wonder: if you could travel back in time, what one piece of advice would she give to 2006 Leona Lewis? "I would say, just listen to your gut", she admits. "Go with that first instinct and don’t take it all so seriously! Just have fun, life goes so fast."

“Candle in the Wind” by Elton John

“I remember seeing the video when I first heard “Candle in the Wind”. Obviously, the song was a tribute to Lady Diana, and her story was so prevalent when I was growing up. My Mum was such a fan of hers and all her humanitarian work, she would always read her autobiography. She would always tell me that she’s the people’s princess, and that she has a lot, but she also does a lot with it and uses her status for good; bringing awareness to a lot of issues and doing all the work with the landmines.

“I love the meaning behind this song. I remember how much my mum adored her, and how upsetting it was when she passed away. My Mum was devastated. I was quite a young girl, but I was still really upset. This song epitomises that light that Diana had, and not only for her, but for anyone that I've lost. The lyrics are so beautiful, and it's a song of remembrance, a song that reminds you that life is so fleeting and so fragile. But, if you can do something good with your life, if you can impact someone positively or just leave the world better than it was when you came here, that will live on.

“For me, the beautiful thing about music is that it can live on beyond yourself. It’s not that I go into a room and I'm like, ‘I'm going to write a song that’ll live on beyond me’, but it is a way of leaving your little mark, you know? I think that’s a beautiful thing to be able to do as an artist. I'm very, very picky about the songs I put out into the world, and sometimes that can be a blessing and a curse. But I want to put out things that are meaningful, that really speak to me, and that will hopefully mean something to the people listening. So sometimes that takes a bit longer than the usual [creative] process, but it's my process, and I have to honour that.

“There are so many songs coming out all the time, and I used to feel like I needed to put some music out to keep up. A part of that realisation gives you the drive to create, but a part of that can create pressure, for sure. I'd say that years ago I would definitely feel a bit of that pressure, but I quickly learned that that is not the way to go for me.

“I need to let myself marinate in what I'm creating and stay true to what I think is good for me. I always have to go with my gut, with anything I do. I always have to go with that very first instinct, so that I don't listen to that pressure.”

“Lovin' You” by Minnie Riperton

“Riperton definitely is a vocal influence for me. As a vocalist, she just sings with such ease and her voice is so light, floaty and airy. I recorded this song, I think around when I was 13 or 14, and I remember how badly I wanted to get that high note!

"She made me realise how you can use your voice in so many different ways - you can use classical elements in head voice, and then you can kind of come down and bring that airiness into your mid-range. She really inspired me as a young vocalist.

“When I was younger my Dad used to listen to a lot of different styles, he was a big influence musically for me, because he introduced me to so much music. He was a DJ and a big fan of ‘70s music. He also loved big female voices too, so he introduced me to different songs and artists like Oleta Adams, Whitney Houston, and Minnie Riperton. The friends that he had around him also influenced me, because my Dad hung around with a lot of musical people.

“My auntie was a really great singer too. Looking at it, I think these artists have all been passed down to me from my family.”

“Pastime Paradise” by Stevie Wonder

“I'd heard his record Songs in the Key of Life, and it would just play every now and again in my Dad's record collection. But I didn't really gravitate towards it until I got older, and I started, probably a decade ago, like really listening to it, and listening to all of the tracks on that record. “Pastime Paradise” was the one that really stood out to me. Maybe subliminally, I was really influenced by Coolio’s “Gangster's Paradise” when I was younger. I knew it was a sample, but I didn't really listen to the original until I got older.

“I think that's what's so amazing about music. You can have this old classic track that can be reworked, and that then means something completely different to someone else. There are so many songs where I'm listening with friends and I'm like, ‘You know that's a remake of the ‘60s original, or a sample from a ‘70s song right?” I'm more interested in the songs that inspired the song, and this is just such a classic.

“The way he used a Hare Krishna chant in “Pastime Paradise” was really interesting, which I thought was fucking amazing and so random. I thought it was amazing that he would use something like that - it was just such an eclectic lyric, an eclectic mash of music - it was just such an interesting sound that drew me in.”

“Love Train” by The O’Jays

“This is one of my Dad's favourite songs and also one of mine. It's funny, for the first dance at my wedding I actually played “Love Train”. Not the first dance with my husband, but for the Dad-daughter dance, that was our song. We made everyone do a train around us and we got everyone to join in. It’s just such a light-hearted song, that breaks down so many barriers.

“This song is one of those love anthems. Like, ‘Come on everyone in the world, let's just join together. Let's just love each other. Let's just be peaceful. Let's just put down the barriers of who comes from where, what colour you are - it doesn't matter.’ I love the message of that song and it's such a groove.

“I think it had the impact of bringing people together through music, which I feel is what the goal is - connecting to people and connecting to yourself. I feel like again, maybe not consciously, it’s almost doing it subliminally, but that song goes in in a way that's like, ‘Wow, this is such a groove, I just want to dance with you to this. I don't care who you are, just dance with me’, you know? That's the kind of feeling it gives me.”

“Greatest Love of All” by Whitney Houston

“Obviously Whitney is such a huge vocal powerhouse, and such an epic singer. And again, with this song, I was very drawn to strong female voice. I think as a kid, I probably gravitated to those powerful females because that's what I wanted to be - a strong, empowered woman. These ladies were doing just that through their voices.

“I was so young when this song came out, but I remember I’d learned every single lyric to it. If anyone was in the house, I'd tell them ‘I'm going to sing my song’, and then I’d sing “The Greatest Love of All” to them, with all of my 6-year-old heart.

“I was just so drawn to it because again, it's such a simple lyric, but it's so effective. Because it's so simple, everyone can understand it and relate to it. It's about an all-encompassing love that’s universally understood, and when you get those simple lyrics that even a child can understand, but an adult resonates so hard with, I feel like those are the best kind of songs.”

“Over the Rainbow” by Eva Cassidy

“Obviously I knew that song from The Wizard of Oz and I have sung the classic version before, but then I discovered Eva Cassidy when I was around 15. I heard someone play her CD in the car and I instantly fell in love with her voice. I was mesmerised by the warmth in her voice and how she took songs and just made them her own.

“Although I'm a songwriter, I'm also someone who takes songs and makes them my own. I found a similarity in Eva Cassidy, where she would rework a song and all of a sudden it became hers. How do you do that? It's amazing how someone can do that with so much power. I love that version, it’s my favourite cover of “Over the Rainbow”. From the warmth of her voice to the message of the song, is it is what it is, it's so beautiful.

“But in particular, the way she made it her own is what really impacted me, and so I've created my own version inspired by her quite a few times. I've performed it so many times now, on big stages, at the X Factor, as an audition piece and at the live shows. It's a song that holds a lot of meaning for me.”

“Hero” by Mariah Carey

“I've been listening to Mariah for years. I was a ‘90s baby, so when I was at that kind of impressionable age, these singers were all around me.

“‘Hero’, for me, is so lyrically strong. Again, it's not relying on anyone, it’s relying on yourself to take care of yourself, to love yourself, and then pass that love onto others. For me, I feel like everything starts with loving yourself and being secure in yourself, and then you can pass that love on. It's a really important message. Also, her delivery is just stunning, I loved the way she sang that song.

“I love listening to romantic love songs, but then there's those little diamonds of universal love that these women have written or sung about - like “The Greatest Love of All”, like “Hero”. These songs aren’t talking about love for a guy or a girl, it’s talking about something much, much bigger.”

“Care Selve” by Handel

“I picked this song because I was classically trained and it's one of the first that I started out with on my classical journey. Not a lot of people know I started off learning opera, I thought I was going to be an opera singer. Handel’s ‘Care Selve’ was one of the first in my repertoire.

“This song kicked off my classical journey, my love of opera, classical, and my love of Handel as well. He wrote some amazing operas and I feel like when I started singing pop music that also allowed me to play with different parts of my voice in songs, using some of my classical training - the same as Minnie Riperton - in my own songs. I use a lot of the head/classical range, and ‘Care Selve’ really put me on that journey.

“From a young age I was practising a lot of soprano work. Now I'm probably more of a mezzo-soprano comfortably, but I can do soprano. But I like the richer tones, so for me I like to stay in the mezzo range. I don't know exactly, but I think I still have a four octave range, it depends on what day you catch me!”

“Weak” by SWV

“I chose “Weak” because it reminds me of my teen years, between the ages of 15 and 16 I would say. I was so obsessed with girl bands at that time and I especially loved SWV. These girls wore baggy trousers, they had the cool hair and the big gold earrings of the ‘90s. I was very influenced by their style, and the fact that they didn’t dress like your stereotypical girl - it was more streetwear inspired, which I just loved.

“Their voices were just amazing, they were such incredible vocalists. Even though they did translate in the UK, it wasn’t as much as in America, but for a girl band of that time their vocals were out of control. Then came En Vogue, and then I guess TLC came off of that SWV vibe.

“SWV influenced so many artists, so much music, and a lot of style and culture at that time too. Their albums were incredible, with such great songs like “Weak” and “Rain”, and so they definitely inspired me as vocalists. At one point I had a little girl band in school and we always sang SWV songs, so they were so influential for me starting out as a singer.

“I actually auditioned for a girl band at one point and I didn’t get in. Everything happens for a reason but man, I was gutted and I really wanted to get that part. It was with a record label too, and I was so excited walking into the audition thinking ‘This could be it! I could get a record deal!’ But it didn’t happen. At the time it was so shit, but now I think back and I appreciate that everything happens for a reason.

“You have to remember that crap stuff happens, but there will be a point where we can all look back and think, ‘Well you know what? That was in the past and this is why it happened’ and you have to try and take a nugget of a lesson from it. And again, remember to just keep going and things will be okay. It’ll all work out in the end.”

"One More Sleep" is out now via Sony