Robert Downey Jr’s Iron Man and Chris Hemsworth’s Thor lead the band of superheroes into another epic comic-strip adventure.

With so many characters jostling for attention, and so many sequel-friendly storylines left dangling, the second joint adventure for the Avengers is a bit puzzling for all but the most committed comic-book fans.

You certainly need your wits about you to cope with the plot, which finds Robert Downey Jr’s wisecracking Iron Man inadvertently creating a rogue peacekeeping robot (voiced with enjoyably sly disdain by James Spader) whose aim is to destroy rather than preserve humanity.

As the Avengers rush about the globe to save the day, the ensuing battles have all the CGI-boosted heft a $250million budget can buy. But, in the end, there are only so many superhero smackdowns a body can take and, in fact, the film’s best moments arise from the tenderly romantic rapport between Scarlett Johansson’s Black Widow and Mark Ruffalo’s Hulk.