Avengers Assemble has been a long time coming. In the four years since Iron Man kick-started what we’re apparently supposed to call the Marvel Cinematic Universe, every fresh offering from Tony Stark, Bruce Banner, Steve Rogers and… Thor… has been ruthlessly scrutinised for clues to the content of the biggest ensemble superhero film of all time. Fans cheered when legendary SF/fantasy guru Joss Whedon joined the project as director, booed at the news of its 3D post-conversion and wept at the prospect of Tom Hiddleston striding about in a cape once more. Well, the wait is over, and guess what? Avengers Assemble is pretty much perfect.

For once, life on earth is pretty quiet. Reformed arms dealer Tony Stark (Downey Jr) is placidly working on his new headquarters, a tower powered by an arc reactor – the same revolutionary power source which fuels his armour when he suits up as Iron Man. Newly-defrosted supersoldier Captain Steve Rogers, once known as Captain America, is tearing through punchbags while he struggles to adapt to a world that’s changed a lot in the last seventy years. Fugitive scientist Dr Bruce Banner is hiding out in Calcutta, trying to stay off the grid and avoid the fits of anger which trigger his transformation into the Incredible Hulk. Finally, hot-headed demigod Thor (Hemsworth) has returned to his homeworld of Asgard after apparently defeating his treacherous brother Loki (Hiddleston). That’s ‘apparently’ defeating…

To the dismay of Nick Fury (Jackson), the covert agent whose secretive organisation S.H.I.E.L.D. once sought to unite these heroes in what was called the ‘Avengers Initiative’, the bitter and power-crazed Asgardian bursts back onto the scene – and the first thing he does is steal the Tesseract, an artefact with potentially limitless power. Fury planned to use the Tesseract as a clean power source, but for Loki it’s the means to his ultimate end… the subjugation of the entire human race. With Loki gathering an extraterrestrial army to back his takeover bid, the abandoned Avenger project could be the world’s only hope. “We’re not a team,” sorrows Dr Banner, “we’re a time bomb.” But will the tentative alliance of some of Earth’s most powerful and emotionally erratic superbeings be enough to avert the coming Apocalypse?

The mere fact that I’ve barely mentioned half the main characters in Avengers Assemble should be enough to illustrate what a hellish time Joss Whedon must have had as director. The Buffy supremo’s challenges were manifold – balancing the larger-than-life Iron Man, Thor and Hulk without giving any of them a distinct lead role, breathing new life into the dull, jingoistic Captain America and Marvel’s token bit of skirt Black Widow (Scarlett Johansson) and stopping Samuel L. Jackson saying “Avenge this, motherfuckers!” every five minutes sound like tasks far beyond most puny mortals. Whilst Whedon might not have his cast’s gleaming armour, however, he’s every bit as gifted as Thor or Cap.

Quite simply, Avengers Assemble is more in tune with the strengths and restrictions of its genre than any other superhero film I’ve ever seen, combining as it does the intelligent scripts of Chris Nolan’s grittily reimagined Batman with Iron Man‘s gleaming wit and the sheer kinetic glory of Thor whilst ducking the latter films’ less flattering labels – respectively, dourness, high-camp flippancy and witless action. A universally excellent cast brings the well-paced and unpredictable story to life – Downey Jr., Evans and Hemsworth play to their strengths as ever, but particular credit is due to newcomer Mark Ruffalo for his understated, endlessly engaging Bruce Banner. Scarlett Johansson is also on excellent form, proving more than up to the challenges posed by Whedon’s passion for genuinely worthwhile heroines after her totally pointless role in Iron Man 2. Even Jeremy Renner, whose S.H.I.E.L.D. super-archer Hawkeye has easily the least screen time of the six heroes, is given chance to shine within a brutally dark subplot and some unexpectedly touching scenes with Johansson. Plus his bow is the SHIT.

Finally stepping out of the shadows after a franchise existence which has hitherto been largely limited to post-credit sequences, Sam Jackson’s Nick Fury is exactly as badass and wise-cracking as you’d expect him to be. It’s also lovely to see some more screen time Fury’s lieutenant Agent Phil Coulson (“Phil? His first name is ‘Agent’!” snaps Stark) – after several films as a functionary, Clark Gregg gets a reasonable serving of limelight and ends up propelling the plot forward at a crucial moment. Finally, Tom Hiddleston (who was the best thing about Thor) once again steals the show as the extravagantly behelmeted Loki – alternately savage, regal and scheming, he is never less than utterly watchable. His rent-a-monster CGI minions are somewhat less impressive, but in truth they’re only there to keep things moving and give the team something to shoot at; Whedon could have replaced them with Furbies and the audience wouldn’t have given a toss.

It doesn’t seem like too much of a spoiler to say that, before going their separate ways, the Avengers do a pretty good job of saving the world. Watching them leave his flying aircraft carrier/egomania fortress, one of Nick Fury’s aides asks the Director how he can be sure they they’ll return the next time trouble looms. “They’ll come,” booms Fury, “because we’ll need them to.” Twelve years after X-Men revised the world’s opinion of superhero films and seven years on from Chris Nolan’s triumphant Batman reboot, Avengers Assemble is exactly the film that this high-concept, high-energy and critically high-risk genre needed. Give it another five years and, with luck, Whedon and his soldiers will assemble once more to set a new benchmark – for now, Avengers Assemble is the superhero extravaganza the world was waiting for.