Christmas ads 2015: Could Sky Movies knock reigning champion John Lewis off the top spot this year?

Each year mega brands vie to make the TV ad that 'owns' Christmas. Adam Sherwin goes behind the scenes as Sky Movies shoots its 2015 contender

Clydee Scrimshaw (Rosie) finds herself transported to a ball, where Cinderella is the star guest

It's a scorching late-summer's day in Budapest, but inside the Origo film studio's gigantic soundstage the scene is rather more festive. Crackers and presents are waiting on a table set for Christmas lunch inside a seamless recreation of a British suburban home.

In a far corner of the vast complex, 60 dancers, elegantly clad in dinner dress and crinolines, are re-enacting the lavish ballroom scene from Disney's recent live-action Cinderella on a set built to the exact specifications of the entertainment giant.

A small English girl darts through the ball scene, desperately seeking to offload an unwanted sprout, until a cry of "Cut!" At which point the action is replayed to a team of British advertising and television executives, tapping away on laptops and in constant contact with Disney overlords.

Word spreads of a potential disaster. A Hungarian extra has posted an Instagram picture of himself, in full Prince Charming regalia, with a message potentially revealing the purpose of a shoot so secret that everyone involved has been required to sign non-disclosure agreements.

This is the high-stakes, borderline paranoid world of the Christmas television advertising campaign, now a keenly anticipated event in the festive calendar – and a battle to the death between bitterly competitive brands seeking to loosen the nation's tear ducts, followed by our purse strings, through ever more heart-rending mini movies.

For many, the Christmas season truly begins tomorrow, when John Lewis will unveil the latest instalment in its sentimental winter stories, accompanied by a doleful musical soundtrack.

Last year's Monty the Penguin clip, evoking "the magic of make-believe at Christmas through a child's eyes", won a prestigious Cannes Golden Lion award for advertising, upping the ante among rivals.

Marks & Spencer and Waitrose are due to follow on Sunday, with research showing that one in five shoppers will have completed part of their Christmas shopping by the first week of November.

The Hungarian shoot is the centrepiece of a million-pound Sky Movies Christmas advertising campaign that is unleashed on social media tomorrow, ahead of a television debut during Saturday night's X Factor live show.

The scenario follows a sprout-hating little girl, who escapes from the dreaded greens on her Christmas table into a magical world in which she interacts with characters from Cinderella, Big Hero 6, Avengers: Age of Ultron and inevitably, the children's favourite Frozen. "Don't just watch your favourite films, be part of them," as the tagline goes.

Even as a crew of feature-film veterans translates Sky's hard sell into 90 seconds of screen gold, gossip turns to competitors' plans to "own" the Christmas ad space. Will Sainsbury's opt for something more traditional after its 2014 First World War "Christmas truce" clip was criticised for exploiting the conflict, despite racking up 17m YouTube views?

Which "on-brand" celebrities will be cosying up to the mistletoe? Last year, a 12-year-old Romeo Beckham wrapped in a Burberry scarf helped boost the fashion label's trench-coat sales. "Everyone is trying to outdo the competition. Some people in the advertising media are talking about it as though it's an arms race," says James Bland, executive producer at Blink Productions, which brought Monty the Penguin to life ("I sign a lot of NDAs") and won the pitch to make Sky's advert.

Director Michael Spiccia captures the first scene

"All the brands are looking to be declared 'the one who owned Christmas'. Every year, all the brands reconsider their approach and try to anticipate what their competition will do. It's about buzz, and getting saturation into the consciousness of people in the UK."

Bland compares the Christmas ad war to Super Bowl night in the US, where brands splash out up to $12m (£7.8m) in order to create a spectacular commercial intervention that is more talked about than the game.

He notes, though, that it is only in the UK that the craft of Christmas television advertising has been elevated to such heights.

Over 80 extras were used for the ballroom scene

Christmas never ends for Simon Robinson, the creative director at WCRS, Sky's advertising agency, which started work on the new campaign in February. It began with a sprout. "We saw at least 100 scripts, but we got a positive gut reaction from the sprout idea. Christmas is almost the perfect time for children, but there's that little dark side, which is the Christmas nemesis, the evil Brussels sprout."

Sky's concept requires its heroine, eight-year-old Clydee Scrimshaw from Nottingham, who was cast after a nationwide search, to be inserted into scenes with Disney properties including Bayman, the Big Hero 6 robot.

Wired up to a "green screen" backdrop, school gymnast Scrimshaw uses the sprouts as grenades to fend off attacks from Avengers' supervillain, Ultron, and has to flee from a spooky Night at the Museum. Hundreds of Hungarian sprouts have been manipulated by the props department to match the size and shape of the average British sprout.

Robinson said: "The ad became a task of 'how do I get rid of these sprouts? How do I avoid eating them?' We knew we had to feature the films Sky screens, too. We had to take the girl into the films and make it feel effortless as a piece of entertainment, not just an ad."

Clydee Scrimshaw takes a break from filming as she wanders backstage

The production values required the hand-stitched original costumes from Disney's Cinderella remake starring Lily James to be rescued from a Madrid warehouse. Disney pre-approved every animated gesture and item of clothing worn by its characters, with the full-length version of the ad primed for a cinema release.

Clydee also has to evade the obstacles placed in her path by Clearcast, the body that clears adverts for broadcast. She must not be shown in great danger or peril, or eat cranberry sauce at the Christmas table, since it is high in sugar. A penguin shown eating a sprout cannot look "disgusted" but must act "surprised" instead.

But even an advert with the highest production values will initially be viewed on the smallest screens. John Lewis dominates the conversation by launching its advert on YouTube before it airs on television. Winning Christmas means having the most shared advert.

Zoe Hughes, head of brand marketing at Sky Movies, says: "Our ad will run on X Factor, but it's almost as if TV isn't the big thing anymore. People talk about whether they've seen the latest ad. John Lewis are clever about seeding their campaign, building a bit of mystique."

That metric – positive buzz – is almost more important than a direct correlation to sales. Monty the Penguin didn't prevent John Lewis counter sales falling by around one per cent in the five weeks to 27 December last year, although online business helped the retailer's revenues grow by 4.8 per cent.

For the creative, such as Michael Spiccia, the award-winning director of the Sky ad, who has previously worked with Baz Luhrmann, "success is all in the idea and the execution of that idea."

Clydee Scrimshaw defies gravity for the Avengers: Age of Ultron scene

Hughes says that the success of Sky's high-profile campaign would be judged by the number of new subscribers and upgrades to Movies by customers. But factors such as "talkability, the number of YouTube views and the press reception" were equally important.

Viewers have an unspoken pact with advertisers, believes Barry Skolnick, Sky's group creative director. "If Sky as a company is arrogant enough to interrupt somebody's TV viewing, the programmes they love, the least we can do is entertain them.

"Sure, we want to sell product, but we're also trying to put the true face of our personality out there. We're an entertainment company. If we can't step up and entertain with our ads it would be a very sorry state."

The second day of shooting in Budapest ends with the extra being reprimanded and forced to delete his errant posting. The tireless Scrimshaw says she can't wait to tell her friends she will be appearing in an advert with her Disney heroes during The X Factor.

But for those locked in the Christmas ad arms race, there's barely time to raise a glass. Skolnick said: "We're talking about the 2016 campaign already. We'll look at what mistakes we've made this year and how can we do better."