Rifling through the script of X-Men: First Class after a series of sturdy, semi-successful Oscar-bait dramas, James McAvoy must have felt that this was his shot at superstardom, the key to worldwide fame, being mobbed on streets and felt up by screaming fans. Why else would he have accepted the part of the not-yet-Professor Charles Xavier, when every working brain cell must have advised otherwise? There is, first, the imminent possibility of being smothered by the shadow of Patrick Stewart, who played Xavier in the earlier X-Men movies with orotund intonations that made the tritest dialogue resonate like Shakespeare.

But a more immediate danger lurks in the person of co-star Michael Fassbender, who is handsome in the dashing manner of a 1940s Hollywood hero and beside whom McAvoy looks like a prim boy scout. Fassbender, playing Erik Lehnsherr (aka not-yet-Magneto) and stepping effortlessly into the super-sized shoes of Ian McKellen, gets the bracing backstory, the opportunity to seethe and simmer and activate every ounce of actorly muscle, and in contrast, McAvoy, perpetually rubbing his temples in order to tap into other people's thoughts, comes off like a milquetoast with a migraine.

As the story of the would-be Magneto, X-Men: First Class is, well, first class, possibly the best attempt at birthing a brooding man of action since Casino Royale stripped away the frills and fancies and dialled James Bond back to the feral Ian Fleming creation, less punster than predator. Unlike the typical summer superhero saga, which is merely heroic, Magneto's story feels mythic. Erik is first glimpsed as a boy in a concentration camp, separated from his mother, and this instantly marks him with our sympathies, especially since the corresponding childhood instalment of Charles plays out in a New York mansion right out of Edith Wharton.

Erik's powers are first understood and later unleashed by Sebastian Shaw (Kevin Bacon), an act that not only turns the boy against the man but also taints this man as a father figure, and when an adult Erik embarks on a mission to finish Shaw, he growls, “Let's just say I'm Frankenstein's monster and I'm looking for my creator.” This is a great character, with just the right blend of pop-culture frivolity and patricidal fury, and Fassbender, fittingly, is the actor who looms largest in the film's final frame.

Erik and Charles meet mid-sea and become thick friends, and the director, Matthew Vaughn, anchors these early scenes with this bond of brotherhood. The film, in these sections, has its tongue firmly in cheek and hops across the globe like a Cold War-era Bond adventure (and Bacon plays the villain, very accurately, like a Blofeld-like megalomaniac).

And then the Cold War actually happens, with America and Russia coming to a head over missiles in Cuba. (Among the many amusing homages to the period is the casting of January Jones, the icy mother from television's 1960s-set Mad Men, as the appropriately named Emma Frost.) The real conflict, unsurprisingly, is between the good mutants (Erik, Charles, and company) and the evil ones led by Shaw.

And the film begins to lose its footing. Fassbender is so magnetic that his appeal to fellow mutants to unite against humankind is more potent than McAvoy's call for temperance. Their face-off is dramatically lopsided, which is a problem in a climactic conflict that's not just between two nations and two species but these two men. The end, though, redeems itself, hinting at the rivals we know from the earlier films — Xavier gets a wheelchair and jokes about losing his hair, Magneto gets a helmet and loses his sense of humour.

X Men: First Class

Genre: Action-Fantasy

Director: Matthew Vaughn

Cast: James, Michael Fassbender, Kevin Bacon

Storyline: The story of how everyone's favourite mutant superheroes came to be

Bottomline: As entertaining a beginnings-story as you could expect