Sweeney Todd: The Demon Barber of Fleet Street, 18

Despite the copious blood and guts, Tim Burton's musical is a strangely moral tale

(Warner Bros)

Slit throats, body parts, cannibalism, gore – now that's my idea of a musical. As pessimistic as Jacobean tragedy and as liberal in its blood-letting as Hostel or any such charnel-house romp, Tim Burton's Sweeney Todd: The Demon Barber of Fleet Street is nevertheless rollicking good fun and, I dare say, an ideal post-Christmas panto for all the family – or it would be if not for the 18 certificate. That seems a bizarre decision by the BBFC since, fountainous though the claret is, you never feel that it's real. In any case, Stephen Sondheim's musical is a profoundly moral work, in which the innocent prevail, the wicked are punished and – well, all right, so a multitude of probably upstanding citizens end up as pie-filling.

Johnny Depp is the barber, unjustly exiled by the wicked judge who debauched his young wife. Returning to London years later – ashen-cheeked and with a white streak slashing across his hair like a lightning bolt of disillusion – Sweeney establishes himself as the quickest razor in town, in a shaving contest with Italian mountebank Pirelli (a show-stealing Sacha Baron Cohen, a popinjay in peacock blue). Sweeney's intent is to slit the throat of Judge Turpin, played by Alan Rickman as a grizzle-chopped voluptuary. But the barber's new ally and would-be inamorata, pie-baker Mrs Lovett (Helena Bonham Carter), has better ideas for how both their businesses can thrive. They may be an evil pair, but they're pioneering in their way: such radical innovation in British cuisine would not be seen again till Heston Blumenthal.

Every frame tells you that Sweeney Todd is a Tim Burton film, although he significantly plays down his fondness for sugary-sour, nursery-tale Gothic: what makes this film so blackly amusing is that it's not played for laughs. The Dickensian London designed by Dante Ferretti has a skyline of hellishly billowing chimneys; the images, predominantly bled of colour by the director of photography Dariusz Wolski, resemble engravings in a penny dreadful. There's a splash of horror-film history too: the ship on which Sweeney returns looms out of the Thames fog, resembling the vessel that carried Dracula in Nosferatu.

Burton and co occasionally break up the colour scheme a bit, notably when Mrs Lovett dreams of a happy, respectable future, sunlit seaside walks and all. Seeing her in bright frills and Sweeney in scowling monochrome, out picnicking, you suspect that Burton is having a little joke about his and his leading lady's home life.

You may find Helena Bonham Carter a little leanly glamorous, if you expect Mrs Lovett to be as matronly as Angela Lansbury, who created the role. But while her fragile singing voice sometimes struggles beneath the torrents of Sondheim's wordplay, Bonham Carter is briskly funny, putting a larky, flirtatious spin on her rag-doll demeanour. She's extremely good in the poignant but sinister scene where the urchin Toby declares his devotion to her: a tear runs down Mrs Lovett's cheek at the recognition that he's doomed, but what's a businesswoman to do?

Depp's Oscar nomination has surprised some, who find his performance a little, pardon me, bloodless. It's not at all: just glowering and introverted, as befits the role of an embittered monomaniac. Can Depp sing? Not strictly: his delivery is a half-speaking Cockney snarl, in the line of David Bowie and Anthony Newley, but he makes it his own, thick with malice and, when necessary, soaring nicely on the end notes.

Along with the familiar faces – including Timothy Spall at his juiciest – there are some fine unknowns. Jamie Campbell Bower is candidly floppy as the naive sailor Anthony, and young Ed Sanders is a magnificent find as Toby: hearing him bellow "Pirelli's Miracle Elixir", you can't help thinking of Jack Wild's Artful Dodger, given the song's pastiche of Lionel Bart oompah.

The staging emphasises a chamber-drama feel, but if you're expecting the Brechtian artifice of the theatrical productions, be prepared for something closer to the lurid realism of Hammer horror. Sondheimites should generally approve, although the recurring "Ballad of Sweeney Todd" is an ill-judged loss.

Otherwise, the film honours the songs, and Jonathan Tunick's lush orchestrations. We get the full beauty of Sondheim's ironies: death hovering about Turpin's chops as he swoons to the erotic ecstasy of "Pretty Women"; Lovett entranced by the shimmer of the music, and of Sweeney's blades. Smart, elegant and more adult than you expect from Burton, Sweeney Todd is a grisly – and gristly – delicacy.