The year is 2017. DC’s Justice League is finally game and set to challenge Marvel’s thus far almighty dominance in cinematic world building. The film bombed. Few emerged unscathed. Gal Gadot shone, of course, but it was franchise newcomers Jason Momoa and Ezra Miller that stole the show. Let’s fast forward. While Gadot and Momoa saw solo outings rapidly release, it’s taken six long years for Miller to win his own run in the sun. Owing to a string of high profile indiscretions and a very public mental health crisis, it may well be his last. Perhaps that’s why Flash feels so strongly like one last DCEU hurrah. There are other reasons – a reboot looms, for one – but some must go unspoiled.

In spite of all going on in real world, Miller is rather good here. Their super-fast Barry Allen has lost none of his peppy vim in the intervening half decade. Right from the off, it is Miller’s ear for the playfully sardonic that sees an alt left opener ape convention. While Batman (Ben Affleck, initially) motors straight into the big guns, Barry’s role is in the clean up – ‘I’m essentially the janitor of the Justice League’ – which here means plumbing and saving a half dozen babies and CGI terrier from grisly deaths, via a vending machine pit stop. To a screaming midwife, Barry recommends mental health services. This, while noting this is not a strength of the League itself. He all but winks to the camera. Such is the humour level of a wit writ script by Bumblebee’s Christina Hodson, which lodges only a few notches below Marvel’s sharper offerings in comic value. Certainly, a decent reel of chuckles pepper the film’s hefty runtime.

The plot itself is relatively straightforward. What opens as Back to the Flashture soon becomes Groundzod Day when a trip down metaphorical memory lane leads Barry into a more literal historic excursion. With his father due to stand trial for the murder of his mother over a decade earlier, a crime he did not commit, Barry hot foots it back in time to save both. Big mistake. What our speedy hero doesn’t realise is that time is like dry spaghetti – just go with it. A splinter in the middle alters not only the trajectory of the future but the path of the preceding past. In saving Mrs Allen, Barry wipes out Aquaman, Wonder Woman and, most critically, Superman. This is a problem. It’s a flurry of the surreal that sees the remainder of the film play out as Man of Steel sans the man himself but with double the Barry Allen.

One more neat twist of the film’s parallel divergence is the switching out of Affleck’s increasingly moribund Bruce Wayne for the older model of Tim Burton’s days at the helm. It’s with a joie de vivre long absent from portrayals of the caped crusader that Michael Keaton soars back into the bat fold. What a joy! Certainly, Keaton has more fun here than Affleck, Bale and Pattinson combined, regardless of the success afforded the films around them. Sasha Calle features too, in a commanding feature debut, as Kara Zor-El’s Supergirl. How the DCEU might have differed had Henry Cavill’s Clark Kent shared an ounce of Calle’s organic charisma.

Much has been made of the film’s shonky cinematographic finish. For all the pizzazz of its electric hues, Flash suffers, it must be said, from a ropey clutch of egregious effects. Andy Muschietti, who directs off the back of success with the It films, might allege the visual kookiness is served with intention but it remains to be seen as to whether Barry’s gurning hamster ball time travelling is meant to win the guffaws it can’t help but illicit. Not that Flash could ever be confused with a film of dramatic heft. It is a facsimile of human drama. A film that understands such stories are meant to hit the heartstrings but is never quite sure how this might be done. The teary finale comes close but only in the wake of a protracted midsection that seemingly forgets Barry’s highly emotional motivations entirely.

Flash instead finds sturdier footing when contented simply by rollicking along, asking audiences only to enjoy the ride. The action is of a weightless, video game quality and none of the narrative stands up to scrutiny. Not that it really need to. The cameos and in-jokes are gorgeous and you can’t go wrong with a shot of Supergirl whacking Michael Shannon’s Zod with a chunk of metal like some sort of intergalactic piñata.