Forget necrotising fasciitis. Theatre suffers from a dangerous condition known as SGS, or Sondheim Guilt Syndrome.

This brain-scrambling disease first manifested after the speedy demise of the London run of Sweeney Todd (starring Julia McKenzie, below). Some reviewers had grudgingly recognised its quality, but most took it for granted. Despite Broadway success and its stature as the only successful thriller-musical (the competition was Carrie, admittedly) the notices generally found its seriousness off-putting. They also wondered whether people wanted to see so gory a piece (not a problem in Hamlet). Enter SGS.

Ever since, every Sondheim revival has led guilt-ridden critics to overlook ropy productions in the rush to praise the pieces themselves. The European premiere of Anyone Can Whistle at Cheltenham was made bearable only by Marilyn Cutts' performance. The Chichester revival of A Little Night Music was less of a reappraisal, more an utter misunderstanding. Sondheim is not famous for giving directors an easy time in rehearsals, but he deserves better.

Sometimes he gets it. If you missed the Hudson/Jones Into the Woods, shame on you. Likewise, the National's Sweeney Todd. Not because it's flawless (it isn't - Donnellan's use of the chorus is curiously unmusical) but because it has passion and power. It closes tonight. An occasion for sadness. And guilt?

(Photograph omitted)