Director Michael Mann, he of Heat and Collateral glory, return for yet more tough guy hilarity with this old-school tale of guns, gals and gangsters

The ever-reliable Johnny Depp ventures into a dark era of modern American history, playing John Dillinger, a notorious 1930s criminal who led a wave of headline-grabbing bank robberies during the Great Depression. Cocky, connected and seemingly unstoppable, his success and penchant for escaping from prisons stands as an affront and embarrassment to the authorities.

Keen to take Dillinger and his cronies down, FBI chief J Edgar Hoover declares a War on Crime, appointing hotshot cop Melvin Purves (Christian Bale) head of a crack unit, tasking him with the job of bringing Dillinger to justice. Employing modern crime-fighting techniques, the case offers the newly formed FBI the chance to become recognised as a national power, and for both Purves and Dillinger their success requires the downfall of the other.

Though a hard man to pin down, Dillinger does have one link to the real world, his girlfriend Billie (Marion Cotillard), a feisty sort who has little fear of her other half’s lifestyle. Left behind while he’s on the run, Billie holds the key to Public Enemy No.1’s capture. With Dilliinger looking for that one big bank job that’ll fund their escape route from America, the race is on for Purves and his boys.

As with all of Mann’s work, there’s a reliance on simmering tension punctuated by violence, yet here the balance feels out of whack. Usually, the characters carry off the film, but here it all feels like the outlines haven’t been filled in. Depp is his usual charming self, which gives Dillinger some appeal, but beyond a cheeky smile and a few soundbites there’s little of interest. Bale fares even worse, his G-Man being nothing more than starchy template, what doesn’t help matters is Bale’s default setting, a stern, unflinching façade that he tends to be sporting whichever role he takes.

More confusing is the film’s inability to decide what it wants to be – Public Enemies is supposedly based on a true story, and seems preoccupied with the historical details of the pursuit, yet plays it loose with actual events. The nature of his relationship with Billie deviates wildly from his real-life marriage – which is fair enough, but as it’s made a key aspect of the film it fudges the veracity.

Though hardly short on action, Public Enemies feels weirdly melodramatic - no matter where the plot turns, it always returns to the bond between the gangster and his moll, passing over the interest in crime-fighting methodology (with its subtext reference to the recent naughtiness of the US government) and the urban folklore the bank robbers inspired.