George A Romero's The Crazies (1973)

Watching George A Romero's original 1973 version of The Crazies it's easy to see where the idea for Danny Boyle's "is it a zombie movie or isn't it?" 28 Days Later came from.

After a military plane crash (which happens before the movie even begins), an experimental bio-weapon - codename: Trixie - gets into the water supply of Evans City, Pennsylvania.

Trixie eventually drives those it infects to acts of extreme violence, either against others or themselves.

These aren't the normal mindless zombies we are used to from Romero's oeuvre, they retain any weapon proficiencies they may have had before infection and gain an amoral knack for turning anything they can lay their hands on into a tool of destruction.

The Crazies opens in media res with a farmer having already killed his wife, then torching his house and attacking his two children.

The fire allows us to meet the main protagonists of the film - ex-Vietnam vet and Green Beret turned high school coach and volunteer fireman David (Will MacMillan), his pregnant girlfriend, doctor's secretary Judy (Lane Carroll) and David's old army buddy and fellow firefighter, the neanderthal Clank (Harold Wayne Jones).

The air is thick with Cold War paranoia and general anti-establishment sentiment as the army moves in - all faceless in their gasmasks and white NBC suits - to try to control matters, but their heavy-handed approach quickly rubs the locals the wrong way and brawling and gunplay ensues.

If the metaphors weren't ladled on heavily enough at one point an infected priest sits down in the road, pours gasoline over himself and sets himself alight - mirroring the acts of Buddhist monks' protesting the Vietnam war.

Meanwhile the scientist dragged in to help the military concoct an antidote is continually hampered by bureaucracy and the top brass have their finger twitching over the nuclear button - to blast Evans City off the face of the planet from a bomber circling above, at a moments' notice if matters get too out of hand.

Throw in the increasing number of infected - driven to insane acts of violence as the man-made virus takes hold - and the military's attempts to maintain order break down as quickly as they are put in place.

David and his posse team up with hippy chick Kathy (Lynn Lowry) and her father Artie (Richard Liberty), who are more a liability than a help in David's mission to ensure the safety of his girlfriend and their unborn child.

While indisputably tense, the special effects of The Crazies are rather dated for a modern audience with most gunshot wounds looking like little more than hits with a paintball pellet, but I suspect it is the psychological nihilism of the story, with its pessimistic ending echoing that of Romero's earlier Night Of The Living Dead, that earned it its 18 certificate.

There certainly isn't the harsh language or graphic gore of the 15 certificate Kick-Ass to worry the sensibilities of any Daily Mail readers who may have accidentally slotted this little grindhouse/drive-in cinema gem into their DVD player.