It would be easy to slam “The Last Legion.” From a historical perspective, it’s certainly bunk. The script, based on a novel by Valerio Manfredi, melds a wacky redoing of the last years of the western Roman empire with the origins of the Arthurian legends. The production strives for an epic feel, but fails to achieve it, looking almost humorously threadbare at points. And the cast, though starry, doesn’t overexert themselves, pretty much coasting along except in the frequent moments when some of them are called upon to engage in acts of swordsmanship and other derring-do.

But criticism on such matters would be rather beside the point. This Dino De Laurentiis “presentation” isn’t intended to be a serious historical film or a “Gladiator”-style adult crowd-pleaser. It’s an old-fashioned boys’ adventure yarn, sort of like something along the lines of Rudyard Kipling’s “Kim” transposed to the dawn of the so-called European Dark Ages. The closest cinematic analogue might be the Ray Harryhausen-inspired “Sinbad” pictures of the late fifties (though minus the animated beasties). As such it’s probably far too tame for most of today’s youngsters, brought up as they are on the high-tech, hyper-propulsive style of things like “Transformers.” But boys between, say, seven and twelve might find it fun, and boomer parents brought up in simpler times may enjoy it too, though (apart from the widescreen images) it probably would serve them just as well on a DVD player a couple of months down the road as in a theatre auditorium right now.

The plot centers on spunky tyke Romulus (Thomas Sangster, from “Love Actually” and “Nanny McPhee”), who, in 460 A.D., is crowned Roman emperor as the last in the line of Julius Caesar. (Actually young Romulus “Augustulus,” or “Little Augustus,” as he came to be nicknamed, has no blood ties to Caesar at all, and became a puppet ruler only in 475, reigning only a few months before being deposed and sent into exile.) He’s to be protected by stalwart legionary Aurelius (Colin Firth), but the royal family is betrayed by their supposed Gothic ally Odoacer (Peter Mullen); Romulus’ father Orestes (Iain Glen) and mother (Beata Ben Ammer) are killed and the boy taken prisoner, along with his mystical tutor Ambrosinus (Ben Kingsley). The captives are taken to the old imperial stronghold at Capri under the cruel eye of Odoacer’s most vicious henchman Wulfila (Kevin McKidd).

Happily Aurelius and his surviving men are on their trail, along with a formidable Byzantine fighter who turns out to be the lovely Mira (Aishwarya Rai), supposedly a warrior from India! They rescue Romulus and Ambrosinus, but not until the boy has discovered at Capri the fabled sword of Caesar, whose holder is prophesied to rule; and—after the defection to Odoacer of the Roman senate represented by Aurelius’ friend Nestor (John Hannah)—the band makes its way to Britain, to enlist in their cause the last loyal legion, the one stationed at Hadrian’s Wall. Unfortunately, not only have Wulfila and his band followed them, but they make common cause with the Anglian tyrant Vortgyn (the masked Harry Van Gorkum), who wants the sword of Caesar for himself. A big battle ensues, which naturally results in the triumph of the good—despite some sad losses—and the defeat of the wicked. And that’s not all: the young Romulus becomes the founder of the line that eventually leads to King Arthur, Ambrosinus is revealed to be a famous sorcerer, and as for the sword of Caesar—well, it winds up encased in a stone under another name.

From historical and literary perspectives, of course, this is all the sheerest hooey, but with eager young Sangster at the center, it’s the sort of adventurous nonsense young boys—who can identify with him—might find exciting. As for the adult actors, they go through their paces with only an occasional knowing wink at the screen; one can imagine people like Firth, Kingsley, Hannah and Glen deciding to take on their roles merely to be in something their young sons, grandsons and nephews could watch with pleasure. And though Rai isn’t exactly a master thespian, she’s certainly physically agile, and will prove eye-balm for older male viewers (even while the romantic subplot between her and Firth will annoy the youngsters in the audience, as such things have always done, and the macho horseplay among Aurelius’ men won’t help but seem forced even to them). Mullan, meanwhile, is almost unrecognizable beneath a burly beard, and McKidd looks—and acts (or overacts) like a young Richard Harris. Fans of “Star Trek” might also keep an eye out of Alexander Siddig (Dr. Bashir of “Deep Space Nine”) as the wily and untrustworthy Byzantine ambassador.

“The Last Legion” is by no means a sumptuous period piece, but cinematographer Marco Pontecorvo, production designer Carmelo Agate, art director Roberto Caruso and costumer Paolo Scalabrino have done what they can with modest resources, and there’s a homely pleasure in watching battle sequences done by throngs of real actors rather than plastic-appearing CGI figurines, however small-scaled and clumsily staged as they might be. Their homespun quality, along with the actors’ often muted performances and the tepid, often plodding pacing, shows that director Doug Lefler is hardly a whirlwind, but with the help of editor Simon Cozens, he at least manages to get through the narrative in about ninety minutes, which is about all even a ten-year old would want.

No great shakes as a fantasy epic, then, but there are far worse movies out there for young boys.