Guy Ritchie’s cheerfully ridiculous Arthur is a gonzo monarch, a death-metal warrior-king. Ritchie’s film is at all times over the top, crashing around its digital landscapes in all manner of beserkness, sometimes whooshing along, sometimes stuck in the odd narrative doldrum. But it is often surprisingly entertaining, and whatever clunkers he has delivered in the past, Ritchie again shows that a film-maker of his craft and energy commands attention, and part of his confidence in reviving King Arthur resides here in being so unselfconscious and unconcerned about the student canon that has gone before: Malory, Tennyson, Bresson, Graham Chapman, John Cleese, Eric Idle etc. Instead, Ritchie launches into an all-purpose tale of medieval brigands and scofflaws. It’s more of a laugh than Antoine Fuqua’s solemn take in 2004.

Arthur and the Round Table knights are more like Robin Hood and the merry geezers, a tale of right lairy thieves, and Ritchie’s story of their supernatural-assisted insurrection against the forces of tyranny cheerfully pinches bits of The Lion King and Gladiator and The Hobbit and Testaments Old and New; and he even has a talking-into-a-severed-ear joke nicked from Reservoir Dogs. It’s unsubtle to say the very least, in the same way that Iron Maiden is unsubtle. But maybe subtlety is the wrong approach. At any rate, Ritchie has his head firmly in the speaker bin, and at one stage an evil character even winces and cringes with a ringing in his ears, as if he has been doing the same thing.

Arthur’s dad is of course Uther Pendragon, played by Eric Bana, who is betrayed by his panto evil brother Vortigern, a pop-eyed, pursed-lip Jude Law. The tiny infant Arthur makes a fortuitous escape with everything but a basket of rushes and finds himself growing up with a right bunch of apple-cheeked cutpurses and associates of ladies of the night by the river in a quaint place called Londinium. It is there that Ritchie unveils one of his hypercaffeinated, hyperdrive speeded-up sequences, taking us through Arthur’s journey from childhood to young manhood in a matter of minutes: the sheer effrontery, and its undoubted breezy skill raises a laugh. Having ensconced Arthur as the emerging young leader of a crew, Ritchie brings in such repertory stalwarts as Geoff Bell (bad guy) and Neil Maskell (good guy) for this den of dodginess, and they are entirely at home.

Wicked Vortigern is ever paranoid about the rumoured youngling who might one day defeat him, and who is the only one capable of extracting a certain sword from a rock that forms the bizarre centrepiece to his Angkor Wat-style medieval palace complex. All the men of a certain age are rounded up and forced to attempt this feat, not knowing what it portends, and when Arthur can actually do it and then gets away, it looks as if he will be able to command a kind of prototypical resistance government composed of disaffected nobles and stout-hearted ruffians, including Bill (Aidan Gillen) and Bedivere (Djimon Hounsou).

But there is no Merlin: a big flaw in this movie. Presumably the famous wizard is being saved up for one of the many followups in the franchise series in the pipeline, which may or may not arrive. (We are still waiting for the rest of those Narnia films, by the way.) What we do have is the Mage, in the form of Astrid Bergès-Frisbey, a person of magic skills and the one female character in the knightly sausage party; she is possessed of a gaunt beauty, and eyeballs that tend to turn completely black in the ecstasy of magic. It is the Mage, who – and it’s a bit of a narrative cheat, this but allowable in a fabular context – can get Arthur and his guys out of a jam. Most impressively, she conjures a gigantic snake, after forcing Arthur to let a normal-sized one bite him. It’s a very creepy, and rather exciting scene. When Merlin turns up, probably in the next film, that is going to be a big showoff role and my money is on Robert Downey Jr.

It’s reasonably good fun and there’s a great “assassination” scene in which the director himself puts in a cameo as a frowning householder. The film rattles along exhilaratingly, if sometimes intermittently, like a fairground rollercoaster that occasionally stops and makes you get out and walk for a few minutes before letting you back on.