Sweeney Todd, Harrington's Pie and Mash Shop, Shaftesbury Avenue

Stephen Sondheim's ever-elastic masterpiece is downsized to largely dazzling effect in its latest iteration, which has been transferred intact to a Shaftesbury Avenue pop-up after premiering last autumn within the surrounds of an actual pie-and-mash eatery called Harrington's in Tooting, south London.

Granted a Soho upgrade courtesy the producer Cameron Mackintosh, Bill Buckhurst's production may not be the most nuanced Sweeney Todd you are ever likely to come across, and some may recoil from having Jeremy Secomb's singularly vengeance-prone carnivore so fully in your face. But as a contrast to the much-lauded West End revival from 2012 and the Emma Thompson/.Bryn Terfel staging coming imminently to the Coliseum, the pint-sized power of the current venture occupies its own transformative position on a Sweeney Todd spectrum that looks set to run and run. (There was yet another Sweeney Off West End last year, that one in Twickenham and starring Olivier Award-winner David Bedella, making four versions of this musical in London within less than three years.) 

One could well call this staging Teeny Todd except that the same diminutive was already applied, famously, to a scaled-back Broadway version in 1989, which proved to audiences then that a 1979 musical theatre chiller conceived on a grand scale could also jangle our nerves if presented in an up-close-and-personal manner. But an intimate Broadway house is quite a different thing from the proposition here, which refocuses the show for fewer than 70 people a performance and turns its audience into Sweeney's customers: you can even have a pie beforehand - lamb, though, not lawyer or curate, at least so far. In terms of Sondheim reppraisals, the only one in my experience to invite direct comparison remains the 2006 Follies at the Landor pub in Clapham, where a 22-strong cast performed nightly to a crowd of 50 or less.

The environment here is the principal occasion rather more than the two leading performances, neither of which makes you view Sweeney or his lovesick accomplice, Mrs Lovett, in fundamentally different terms. Secomb's razor-wielding Benjamin Barker must rank amongst the most monomaniacal this part has ever seen, and his obsessiveness comes matched by a lung power that suggests, rather deliciously, that this singing actor would be equally at home on the Coliseum stage. Siobhan McCarthy, an original cast member of Chess and Mamma Mia!, doesn't always hit the notes dead-on, but her husky-voiced Nellie (pictured above with Secomb) is considerably more beautiful than usual, and as the pair's desperation grows, her eyes acquire a shimmer to match the glistening razors that Sweeney values above all else - as Mrs Lovett will learn to her cost. 

It's the supporting cast that really brings Buckhurst's vision of the piece home in marked contrast to too many Sweeneys over time that have privileged star casting at the centre and left everyone else to fend for themselves. Seen in close-up, for instance, the young Johanna is no longer the cloying soubrette of old but an increasingly anxious songbird desperate to flee the cage of Judge Turpin's ruthless (and, in Duncan Smith's excellent performance, nicely understated) devising, and Zoe Doano - the lone addition to the cast following last autumn's run - sings the part spectacularly well. So does Ian Mowat's falsetto-prone Beadle Bamford, a snivelling figure - and a dab hand at the piano, to boot - who could have stepped out of the pages of Dickens and who embodies in a single glance the hypocrisy that fuels one of the many themes of a musical long remarked upon for its social conscience. (The final sequence memorably suggests that all of us in our own way are Sweeney.) 

That level of performance continues down the line. Warming up the crowd beforehand like a carnival barker about to preside over his own carnage, Joseph Taylor (pictured left) is the freshest-face Tobias imaginable, his cherub cheeks at telling odds with the depravity his character will soon encounter. Nadim Naaman's robustly sung Anthony brings unfeigned passion and purpose to a role that can often seem rather wet, and it proves an inspired idea to have Kiara Jay double as both the erotically suggestive Beggar Woman and the duplicitous, none-too-Italian Pirelli: Jay does both roles more than proud, even if it is left to some notably helpful bar staff to actually pour the Pirelli's miracle negroni at the interval. (The drinks come appropriately themed.)

Musically, Benjamin Cox at the piano does yeoman service, his fleet command of the score buttressed at various moments by the atmospheric additions of a clarinet and violin - there's a wonderful quaver from the strings after the Judge is got rid of - and Joshua Richardson's sound design provides an orchestral palette all its own, the charnel house of Sweeney's lunatic imaginings here suggested aurally as opposed to visually, just as the occasional blood-stained smock speaks volumes about what has happened offstage that in other larger productions we would see occurring in front of us. (I love the way in which, too, a firmly positioned broom comes to represent the locked door behind which Johanna has been immured.) Would one want every Sweeney Todd done this way? No, since part of this musical's achievement in full flight has everything to do with its surging wall of sound. But on its own terms, at once revisionist and remarkable, the occasion is indispensable. "I'm full of joy," or so Secomb lets rip as Sweeney moves towards his triumphalist reckoning, and those brought face-to-face here with his fury - not to mention his food - are unlikely to disagree. 

• Sweeney Todd at Harrington's Pie and Mash Shop, 39-45 Shaftesbury Avenue until 30 May