Deborah Voigt will doubtless always be remembered as the American soprano who underwent gastric-bypass surgery in order to lose weight so as to lend both glamour and theatrical veracity to her art. The controversy that still rages over her much-publicised decision has paradoxically ensured that we now define her primarily in terms of shape rather than song, a fact which Voigt herself also seems keen, on occasion, to encourage. "This is my first time in London since that little incident," she told the audience, showing off her transformed, curvy figure. Her fans whooped delightedly.

Mercifully, Voigt's artistry remains more or less intact. Her once-beautiful sound has hardened of late - the product, one suspects, not so much of surgery as of the taxing regime of Wagner and Strauss she sets herself in the theatre. Away from the lofty stage persona, she is a fine, engaging recitalist, conquering with a mixture of charm, wit and world-weary urbanity.

In Respighi's Nebbie, she filled the auditorium with a superbly controlled crescendo of sound. Her Strauss isn't as rapturous as it once was, though a group of early Verdi songs revealed just how dexterously her voice still moves at speed. She has also taken to cabaret of late, superbly it would seem, and she closed with Broadway songs - a heartfelt Somewhere from West Side Story, and, best of all, a performance of Can't Help Lovin' Dat Man of Mine that was deeply touching in emotional truth.