The demon barber of Fleet Street is back in town, and those of a nervous disposition are advised to sit well away from the front stalls at the Festival Hall. There will be few sights in the West End this summer more terrifying than that of Bryn Terfel leaping into the audience, gleefully searching for his next hapless customer – his face locked in a psychotic leer, his voice like thunder, his razor slashing like a scythe.

The Southbank Centre’s production of Stephen Sondheim’s dark, satanic melodrama is billed as semi-staged. The text has been given what Sweeney himself might call a neat trim (losing the Judge’s nasty anthem to self-flagellation is no hardship). There is no scenery, costumes or even the usual spurts of ketchup as Sweeney’s razor embarks on its enthusiastic orgy of serial revenge. Presumably the Southbank management did not want splodges on its pristine new platform.

But what David Freeman’s staging lacks in accessories it more than supplies in energy. A brilliant young ensemble from the Guildford School of Acting evokes a London full of potential Sweeneys: malignant, demented, cruel. At the end all the singers pull out razors and slash their own throats. It’s a shock that Freeman has concocted before (in his production of The Beggar’s Opera, back in the 1980s, everyone produced a noose and hanged themselves), but it effectively caps a performance in which the chorus’s words and movement are as sharp as Sweeney’s shaves.

They are backed by a lively London Philharmonic Orchestra, tucked away to the side and immaculately conducted by Stephen Barlow. But the show is rightly dominated by two tremendous performances in the centre of the stage. The first is Terfel’s. Opera purists may regret hearing the mightiest Wagnerian voice of our age piped through amplification. But what a terrifying embodiment of malevolence! It’s all the better for being gradually unleashed, like a gathering storm. Maria Friedman provides the perfect foil as a joyously amoral Mrs Lovett, proud maker of “the worst pies in London”. Her comic timing is immaculate and her diction superb, especially in that show-stopping, macabre waltz Have a Little Priest, in which she whips up a froth of sexual frenzy for Sweeney.

Round them are suitably grotesque cameos, notably Philip Quast’s smarmy Judge, Steve Elias’s creepy Beadle, Adrian Thompson as the caricature Italian barber Pirelli, Rosemary Ashe as the crazed Beggar Woman, who is more than she seems, and Daniel Evans as the simpleton Tobias, who finally dispatches Sweeney with his own razor. Emma Williams gives a nicely frenetic performance as the repressed Johanna, though she sometimes raced ahead of the beat; and Daniel Boys is an appealing Anthony.

Possibly the most blackhearted Broadway musical ever penned, Sweeney Todd is still an acquired taste. And it’s not exactly stocked with golden melodies. But you are unlikely to see it hurled out with leaner, meaner incisiveness. Two further performances today.

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