Back during the press tour for the original Transformers, Michael Bay talked about how when Steven Spielberg (who produced) called to suggest him as director he said there was no way he was doing a stupid toy movie, only agreeing when he realised he had his way in – a boy and his first car.

Ask any cigar chomping movie mogul (from a past age, there aren't many left) and he'll tell you the audience needs a way into the story. Sam (Shia LeBeouf), was Bay's way in, bridging the gap to the business at hand of giant CGI robots beating hell out of each other and blowing shit up.

Writer Alex Garland and director Danny Boyle may well have used the character of Spike (Alfie Williams) as a way into this story, knowing we as the audience would latch onto the tale of a young boy forced to grow up too quickly in a cruel world.

Unfortunately, where Bay knew he was making a movie about robots blowing shit up, Boyle forgot Spike's family travails was only the way in, not the story. He was there to make a zombie movie, but you've never seen a zombie movie not only with such a low number of zombies but of activity altogether.

Spike lives with his Dad, the scruffy but loving Jamie (Aaron Taylor Johnson) and mother Isla (Jodie Comer), who's so sick with something or other she spends her days upstairs in bed going between near-comatose and flying into rages.

It's 28 years after the outbreak of the rage virus that's seen the British Isles quarantined from the rest of the world and Spike has come of age, so it's time for his Dad to take him to the mainland to scavenge and hunt for infected, across the causeway connecting their idyllic Scottish island home to the mainland which only appears at low tide and keeps them otherwise isolated.

They make the trek and Jamie teaches Spike how to look for the supplies that aren't already picked over as well as take care of any infected they find with a bow and arrow, and the first third of the movie is an effective scary action thriller as they're set upon by more of the monsters than they intended, missing their window to get back and having to hole up in an abandoned house.

But with a massive flock of deer who've bred unchecked thundering across the landscape and one of the evolved infected – the massively-built and virtually unstoppable alpha – standing on a nearby hill lying in wait, their hiding place is soon compromised and they have to make a break for it, sprinting for the causeway even though it's under a foot or so of water and with the alpha hot on their heels.

Once they're back in their village, Spike is a hero and things go back to normal, although he can't forget the campfire they saw from their hiding spot out in the wild. His father says it belongs to a guy who used to be a doctor but is now insane, refusing to discuss it further, but Spike desperately wants to help his mother and sets about finding the doctor to ask for his help.

Thus ensues the longest, dullest second act in recent memory as he sets a diversion at home and takes his mother across the causeway to the mainland through very dangerous territory for what he thinks is his only chance to help her.

There are a few zombie scenes including a well done one with an alpha chasing them through the ruins of a train, although the enormous zombie cock is a considerable distraction (I understand all their clothes would have rotted away after three decades but come on Alex, couldn't you think of something?

There's also an aside about a Swedish squad of paratroopers, the last surviving member of which Spike and his mother connect up with to help them reach the doctor. But once they get there, there's not nearly enough zombie action, terror or violence in a supposed zombie movie.

Kelson (Fiennes) is perfectly sane even if he slathers himself with iodine because it puts the infected off and has constructed a series of enormous towers out of the bones of the dead he's found everywhere, treating them with a particular reverence that's never really explained.

He has an awful diagnosis for Isla, they take care of that (no spoilers) and that's pretty much it. Spike goes back home to leave the interloper they've picked up along the way (again, no spoilers) at the village gate and goes back into the wilderness to teach himself how to survive alone.

Then, just when you think it's going to have the dullest finish ever after the dullest second half, Spike is attacked by a small horde of infected running towards him and is rescued by a gang of roaming vigilantes, one of whom is the young boy from the opening coda of the film that sees his home attacked and goes on the run in the apocalypse's opening days.

Today, both he and his teammates all look like a panto costumer's idea of a bad Scandinavian parody, taking out the horde with stylish weapons and techniques, and then it's all over. Maybe Boyle was trying to say something with such a whiplash, tacked-on ending, or maybe he was answering your prayers by that point that something happen – you don't even care what.

It can be argued 28 Days Later sparked off the zombie craze that's continued to this day as much as any other, leading directly to shows, movies and games like The Walking Dead, Train to Busan and The Last of Us, which makes this inert, disjointed effort even more disappointing.