A British/American venture, the film stars Louis Ashbourne Serkis, Tom Taylor, Dean Chaumoo, Rhianna Doris, Angus Imrie, Rebecca Ferguson, and Patrick Stewart.

[5] The plot follows a young boy who finds King Arthur's legendary sword Excalibur and must use it to stop an ancient enchantress from enslaving the world with help from his classmates (and former bullies) from school.

Despite receiving positive reviews, the movie underperformed at the box office, with estimated losses for the studio ranging as high as $50 million.

The boy reveals himself to Alex as the wizard Merlin, capable of aging backward, but will occasionally shift into his elder Arthurian form.

The Mortes Milles only appear at night and can only be seen by Alex and those he has knighted, but an upcoming total solar eclipse will enable her to emerge fully into the world.

As Lance and Kaye start to leave, Alex calls upon the Lady of the Lake, whose arm emerges from the water and restores the sword.

In desperation, Alex tells her everything that has happened, then stuns her by summoning the Lady of the Lake into the bathtub, where he regains Excalibur.

Merlin casts a magic spell to pull Morgana from the world, and Alex decapitates her as she vanishes, dispelling all the demons.

[8] The visual effects were provided by DNEG, Rodeo FX, Peerless and TPO VFX, and were supervised by Joel Green, Antoine Moulineau, Laurent Gillet, Marc Hutchings, Jack Hughes and Frazer Churchill.

[10] Following its initial performance, it was announced the film was expected to lose the studios around $50 million, taking into account its high marketing costs.

The website's critical consensus reads, "The Kid Who Would Be King recalls classic all ages adventures – and repurposes a timeless legend – for a thoroughly enjoyable new addition to the family movie canon.