The Kid Who Would Be King pulls contemporary adventure from the stone of legend.

Opening with exactly the same set-up and opening thematic point as “Justice League”, Joe Cornish takes the idea of a country and a world which has lost hope and, with a keen eye for contemporary resonance, weaves a wonderfully affirmative and inspirational tale from the ancient cloth of legend and the modern social fabric of present-day England.

Alex (Louis Ashbourne Serkis) thinks he’s nothing special until one day, while hiding from a pair of school bullies, he stumbles into a building site and pulls the mythical sword Excalibur from a stone. Suddenly, he finds himself charged with opposing the wicked sorceress Morgana (Rebecca Ferguson). With the help of Merlin (Angus Imrie, and occasionally Sir Patrick Stewart), Alex must take up the chivalric code of King Arthur and unite his friends and enemies to defend the Kingdom from enslavement and despair.

There’s something gloriously old-fashioned about “The Kid Who Would Be King” and it’s the fact that it’s made explicitly for kids, free from the knowing irony that seems to have become an indispensable part of family entertainment these days. Cornish knows his audience and nails their perspective beautifully, keeping the story simple and straightforward without skimping on the action, spectacle or scares.

It acknowledges the state of the world as it is now without coming off as heavy-handed or moralistic and while you’re free to read into it whatever metaphors best suit your point of view, its overriding message is clear: our children deserve a better, kinder world than the one we’ve created for them.

Not that the film is concerned with getting bogged down in that, not when there’s swashes to be buckled, quests to be pursued and courage to be screwed to the sticking place. There’s an abundance of imagination on offer, from the clever subversion of the staples of Arthurian legend through a suburban prism to the delightfully idiosyncratic way that Merlin’s spellcasting is carried out and the creature design and special effects remain just the right side of scary to delight rather than distress kids of all ages.

The adult characters are, as they should be, superficial caricatures so as not to steal focus from the kids although I will say that Alex’s head teacher, before she’s ensorceled by Merlin’s charms, has one of the worst policies on bullying I’ve ever heard.

Charming, exciting and slyly uplifting, “The Kid Who Would Be King” is a gratifyingly wholesome family adventure, proudly and defiantly counterprogrammed against these cynical times. On the strength of his ability to blend sci-fi and fantasy with a quintessential Britishness (see also his previous directorial effort “Attack The Block”), when the BBC are looking for a new “Doctor Who” showrunner, they couldn’t do much better than offer Cornish the keys to the TARDIS.