An illustrious British boarding school becomes a bloody battleground when a mysterious sinkhole appears at a nearby fracking site, unleashing an ancient subterranean species upon the students and faculty.

On paper, Slaughterhouse Rulez sounds amazing – a comedic British creature-feature with some nifty practical effects and a great cast, including Simon Pegg, Nick Frost and Michael Sheen, that is also the debut film from Stolen Picture; a new production company founded by frequent collaborators Pegg and Frost. Sounds like a recipe for a future cult classic, right? Unfortunately, the sheer awesomeness on paper struggles to translate to screen and what we’re left with is a mixed bag that ranges from awkwardly unfunny to brilliantly charming to gruesomely violent, and everything in between.

Slaughterhouse Rulez follows Don Wallace – a teenager from a working class family from up North who manages to secure a place at one of the most illustrious and imperialistic boarding schools in Britain. He is apprehensive, but doesn’t want to let his overbearing mother down, and decides to honour her wishes; a decision he will soon come to regret. Upon arrival, he immediately realises he doesn’t belong and is quickly introduced to a wide range of students, all of whom conform to a strict hierarchy that has existed for generations. There are four different houses and your success at the school is essentially dependent on which one you’re placed in. It paints a very bleak, albeit comedic picture of what it is like to attend an upper-class British boarding school. Of course, Don is placed in House Sparta; the house for “outcasts” who “do not belong”.

What follows is an overlong introduction to the school, the students and its faculty. While the filmmakers should be commended for trying to enrich their characters and give audiences enough time to connect with them, the truth is that only a handful of them are interesting enough to engage you, leaving much of the first hour feeling empty and frustrating as you’re left waiting for something fun to happen and this is the biggest issue with Slaughterhouse Rulez. The synopsis would lead you to believe you’re about to watch something wildly fun and entertaining, but it takes so long to get to the fun stuff that by the time it arrives, you have disconnected and tuned out a little. Thankfully, the final thirty minutes or so are fun enough to save Slaughterhouse Rulez from being a total bust, but one can’t help but think of how much fun it could have been if the filmmakers had trimmed the fat a little and streamlined the story into something smaller and more engaging.

The cast are all game and deliver some fun performances, with Hermione Corfield, Isabella Laughland, Kit Connor and Max Raphael rounding out the main cast of heroes who are pitted against the unspeakable evil that’s unleashed at the nearby fracking site. They’re a fun group of characters and for the most part, play their roles with tongues placed firmly in cheeks and have some fun with their work. Simon Pegg and Nick Frost provide some excellent support to the main story, resulting in some of the funnier moments in this inconsistent little movie. Pegg plays Meredith Houseman, the head of House Sparta, who is so broken hearted after the love of his life has immigrated to Africa that he can’t help but let it impact on every aspect of his life, including his teaching. Nick Frost plays Woody, an environmental activist-come-drug-dealer who resides in the woods surrounding the school and is at war with the fracking site for polluting the environment. Of the two, Frost and his impeccable comedic timing is wildly underutilized but still provides the occasional fun departure. Tom Rhys Harries is a stand out as the school’s resident psychotic douchebag, Clegg – a despicable character who is played with such dead-pan seriousness that he could quite easily appear in a much more serious movie and still be as sinister as he is here. But the true standout is Michael Sheen, who seems to be having the most fun out of everyone in the movie, chewing up the scenery as the hysterically dim-witted head master who has clearly only got to where he is because of his ancestry. He infuses his performance with a cheeky flamboyance and a knowing wink to the audience, emerging as one of the only reliable sources of genuine laughter in the entire movie.

The creature work is actually pretty solid and the CGI, while nothing ground-breaking, is good enough not to be distracting. The creatures, which resemble giant reptilian rats, really shine with the use of practical effects and animatronic puppets – all of which look great and help add a sense of realism to these other-worldly creatures.

Considering who’s involved, Slaughterhouse Rulez should be a lot funnier than it is. It isn’t unfunny per-se, but it does struggle to become anything more than just moderately humorous and that’s a real shame, because with a healthy dose of big laughs to accompany its violent monster mayhem, Slaughterhouse Rulez could have been something pretty damn special. As it stands, Slaughterhouse Rulez is a good enough way to pass 104 minutes, while simultaneously feeling like a bit of a wasted opportunity.