This month marks the 25th anniversary of Mariah Carey's iconic anthem 'All I Want For Christmas Is You' and, as she cuddles up on the sofa with her beloved Jack Russell Cha Cha for our chat in her 10,000-square-foot, peach-coloured Beverly Hills mansion, Mariah is feeling nostalgic. "I’m sitting here and thinking about it – I’ve been looking for pictures from that original photoshoot, which was like me in the snow in that little Santa suit. It became the first song that I wrote for that album."



So how do you write one of the classic Christmas songs? "I just sat down, decorated a little tree and put on It’s A Wonderful Life and tried to get into that mood. Then I sat in this small room with a keyboard and started doing little melodies and stuff. I was going over all the things I think about at Christmas time that make me happy and how to turn it around and make it into a love song."

The song brought with it an equally iconic video which, of course, sees Mariah cavorting around in the snow and tossing around presents with glee. “See me in the snow in that little Santa suit? That wasn’t a studio, that was a real moment,” she says proudly. “I was freezing cold, my hair was frozen, it was outside in a snowy field [in New Jersey], and I’ll just never forget it because there were real reindeer.” But if you’re wondering if MC still dons that Mrs Claus outfit every holiday season, prepare to be disappointed. “I don’t know where it is! That was one of the first things I had done in my career, so I didn’t realise, ‘Oh, save these things because one day it might be something you want’. But we’re going to have another one made, I think.”

One of the best-selling tracks of all time at 16 million copies, the song has contributed an estimated £48 million to Mariah’s merry multimillion-dollar Christmas empire, with a reported £400,000 rolling in in royalties every year. So popular is it still that it was played 10.8 million times on Spotify last Christmas Eve, setting a new one-day streaming record, and has been covered by everyone from Ariana Grande to My Chemical Romance, Justin Bieber to K-Pop girl band Cosmic Girls.

When it comes to reflecting on the song’s anniversary, Mariah is, of course, as wise as ever. “I don’t acknowledge time,” she declares. "The more I hear [that it’s turning 25], the more I freak out. I’d rather just say it feels like it’s going to be a great anniversary for the album. We’ll call it a birthday. It’s not that it scares me, it’s just if you don’t acknowledge time, you don’t have to deal with it.”

In the 25 years since 'All I Want For Christmas Is You' first warmed hearts, Mariah has morphed like a butterfly into a kitschy beacon of yuletide joy for her devoted fans, AKA her “Lambily”.

But her rise to Undisputed Queen of Christmas hasn’t been easy and the superstar is excitable and often emotional as she opens up about her holiday-season experiences as a child. “Growing up I had a very dysfunctional family,” recalls Mariah, who was raised in Long Island, New York, with divorced parents, siblings she no longer speaks to, and financial challenges. “I always wanted to have a really good time at Christmas and they would ruin it, so I vowed in my own life I would make sure every Christmas was great.

“I want to make it magical for my kids. You know, I think it’s this kind of childlike love of Christmas that saved me. I go through so much all year long just to have a great Christmas.” As we say our goodbyes – Mariah’s eight-year-old twins Moroccan and Monroe are due home from hip-hop dance class at any moment – she pauses. “I enjoyed that so much, thank you. I think everybody should spend Christmas with me because it’s a great experience.”