Olivia Colman will narrate the film, with Matt Smith (The Crown) providing the voice of the hero, Superworm. They will be joined by Rob Brydon (Gavin & Stacey) as the Crow, and Patricia Allison (Sex Education) as Butterfly, with the announcement of other cast members later in the year.

The half-hour special will follow the super-strong titular hero Superworm, as he lends his useful length to rescue other insects and animals from accidents. He works in a dream team with Butterfly, who rescue a beetle from falling down a well and save a baby toad from an accident, but Superworm too often takes all the credit.

Disaster strikes when the wicked Wizard Lizard sends his servant Crow to kidnap Superworm because of his special skills. Butterfly must convince the other animals to help save Superworm, but will they come to the rescue in time?

Olivia Colman said: “This is such a lovely project to be involved with. When reading the script, and imagining all those goings on at the end of the garden, I could really get a feel for the pure fun and joy that the film will bring. I’ve always loved these charming productions at Christmas and I’m delighted to be voicing the narrator.”

Matt Smith added: “I’m delighted to play the part of Superworm! And join such a fabulous cast of actors, artists and storytellers. What fun to be part of the BBC's Christmas line up in this great children’s tale.”

Superworm will air on BBC One and BBC iPlayer over the 2021 Christmas period.