LET ME tell you, you don’t want to be on a passenger plane with zombies aboard. The chaos is worse than the scramble for seats on a budget airline. And Ryanair don’t employ Brad Pitt to ride shotgun and ensure free passage up the aisle for the drinks trolley.

Happily for those uninfected travellers on the Belarus Airways flight to Cardiff, Pitt’s UN investigator Gerry Lane is ready to help passengers prevent the crazed undead from bursting into business class.

He’s a handy man to have around in a crisis (bitten by a zombie? Don’t worry, he’ll cut off the infected limb before you bite off more than you can chew). This is definitely an emergency as the entire world has dialled 999 as World War Z – yes, the Z stands for Zombie – breaks out.

These aren’t the undead we’re used to seeing. They don’t stumble around, arms outstretched, skin blotchy and peeling. These are fast and furious. They race around, leaping on people, having a bite and then they’re gone, leaving the victim to return to life after limb-twisting contortions.

Pitt, his wife and two kids flee the carnage in Philadelphia (played by Glasgow) and hide out in a tower block until a UN helicopter can rescue them in the nick of time.

In return for a safe bed for his family aboard a zombie-free ship, he agrees to undertake that good old movie plot device A Very Dangerous Mission that takes him to Korea, Israeli and, believe it or not, Wales.

The zombie flight crashes (well, he did throw a grenade at the flesh-biting passengers) but he survives, having had the foresight to fasten his seat belt after blowing a hole in the side of the plane. He heads to the WHO lab (World Health Organisation, not the Doctor) to mix an antidote to the zombie virus.

After a four-star first hour WWZ slows down into three-star territory, eschewing a grand no-holds-barred showdown for a suspenseful scene in which it gets personal between Gerry and the Zombies.

There have been tales of extensive re-shoots of the ending and what they’ve come up with really doesn’t cut the mustard. It allows Pitt to save the world more or less single-handedly, but I wanted more of the impressive crowd scenes as a zombie cast of thousands swarm up and over the walls built around Jerusalem like an army of ants.