Marks & Spencer has unveiled its Christmas advert featuring the work of two fairies who have already been spreading some seasonal joy.

The launch of the advert follows an undercover social media campaign that saw the Twitter-based duo @TheTwoFairies amass 12,000 followers by this morning.

The campaign explains why children at Landewednack Primary in Cornwall found their school mysteriously covered in a fresh fall of snow and why a number of people received random gifts through the post.

M&S said it had used social media networks to track down people who were wishing for certain things and delivered the gifts, leaving only a calling card citing @TheTwoFairies #FollowTheFairies.

The retailer, which declined to reveal how much it had spent on the campaign, said the two fairies "bring to life" its traditional Christmas strapline Magic and Sparkle.

Set to the version of Fly Me to the Moon by American artist Julie London, the ad shows Magic and Sparkle gifting snowfall to children stuck inside, adorning grey washing lines with glittering party dresses and sparking love between a lonely pair.

M&S executive director of marketing and international, Patrick Bousquet-Chavanne, said: "The magic of Christmas is how it brings out that little part in all of us that wants to believe in the extraordinary. It's a moment to escape the realities of every day and give in to the joyfulness of the festive spirit.

"We wanted to capture that feeling and bring Magic and Sparkle to life in a fun and light-hearted way that spreads a little cheer."

The ad will air on M&S' social media channels from midday today and on television during this Saturday's X Factor on ITV1.