It’s been almost 30 years since John Landis made An American Werewolf in London, but if Burke and Hare is anything to go by, he still adores Britain and its actors as much as they adore him.

The evidence of this mutual attraction isn’t just the casting of Simon Pegg and Andy Serkis as Edinburgh’s notorious bodysnatchers, or of Tom Wilkinson, Jessica Hynes, and Ronnie Corbett in supporting roles. No, what’s striking is the way that Landis has cast famous Brits in even the smallest parts. Bill Bailey has about four lines, Reece Shearsmith has about three, and they’re ubiquitous compared to Christopher Lee, Jenny Agutter and Stephen Merchant: the man who co-wrote Extras is essentially an extra himself. Presumably, these luminaries were queuing up for the chance to work with the director of Trading Places and The Blues Brothers, and he was delighted to work with them. But aren’t there more important factors to consider when you’re deciding on a film to direct or act in … like, for instance, whether the script is any good?

The main problem with Burke and Hare is that it never quite figures out how to turn a true story of mass murder into a comic romp about a pair of loveable rogues. It starts promisingly enough, with the Northern Irish anti-heroes trying to scam a living on the streets of Auld Reekie. Hare’s wife (Hynes) runs a boarding house, and when one of the lodgers dies, they sell the body to a preening surgeon, Dr Knox (Wilkinson), who needs a steady supply of cadavers for his anatomy classes.

But if Hare (Serkis) is sure of what to do next, the film definitely isn’t, so it drifts away from Burke and Hare’s killing spree, and towards, well, more or less everyone else in Edinburgh. Principally, there’s Burke’s love interest, Isla Fisher, putting on a not-too-painful Scottish accent as a showgirl who plans to stage an all-female production of Macbeth. But there’s also a crime boss (David Hayman) who demands 50 per cent of the duo’s ill-gotten gains, a surgeon (Tim Curry) who hates Dr Knox, and various other characters who don’t serve much of a purpose – and that’s even before we get to cameos by William Wordsworth and an anachronistic Greyfriars Bobby.

The screenplay is by Piers Ashworth and Nick Moorcroft, the writers of the recent St Trinian’s movies, and they’ve taken a similar chuck-everything-at-the-wall-and-see-what-sticks approach. But in among all of the many guest stars and sub-plots, it’s hard to see what the film is actually about. The Burke and Hare we’re shown aren’t particularly villainous, but they’re not heroic, either.

Their misdeeds aren’t particularly hilarious, but nor are they very scary. The idea seems to be that because they’re cheery fellows played by likeable actors, we’ll care about them no matter what they do. And, to be fair, that’s sometimes enough. The gleeful grisliness makes for some funny moments, and there’s a nicely spooky Halloween atmosphere, due to the location shooting and the ever-present smoke machine. Burke & Hare is best described as a Carry On film, without the rude puns. But then, what is a Carry On film without the rude puns?