OPERA / Lost emperor: Tess Knighton on John Eliot Gardiner's version of L'incoronazione di Poppea

In this Monteverdi anniversary year John Eliot Gardiner and his English Baroque Soloists have toured Europe with concert performances of L'incoronazione di Poppea, so that, by the time it reached London on Wednesday, it was well and truly sung in, and ready for live recording by Deutsche Grammophon. Gardiner's is a characteristically strong view of the piece, but there were two not insubstantial drawbacks: first, the sometimes heavy-handed cuts that had to be made (to fit the work on to three CDs?); and second, some rather mixed casting.

There is nothing inauthentic about cuts in 17th-century opera, and it is clear from surviving sources that performances of Poppea varied considerably from one theatre to another. But here the pruning was sometimes so severe that the underlying dramatic thread was placed in jeopardy. The gods were all but excluded; they may seem anachronistic, even bizarre, today, but their appearances, and more importantly, their commentaries on the action are integral to the concept behind Busenello's libretto. Without these divine interludes, the pace became almost frenetic, and the same was true of the scenes with Seneca, and even the later exchanges between Poppea and Nerone.

The casting was both brilliant and flawed. Anne Sofie von Otter was simply stunning as the Emperor's rejected wife Ottavia: by turns pitiful, noble and vengeful, she delivered the text in an impassioned outburst of song - the very essence of Monteverdi's 'recitar cantando'. Sylvia McNair was equally brilliant as Poppea: her suspensions were the most voluptuous I have ever heard. Michael Chance's Ottone was less flamboyantly dramatic but still very fine, the vocal lines beautifully sculpted, the rhetoric controlled but telling.

The rest of the singing was less secure and, at times, decidedly patchy. The cast included a number of Italians whose good voices did not necessarily mean that their words were any easier to make out. But the biggest disappointment was Nerone, the American soprano Dana Hanchard. It could be regarded as a misfortune to be outsung by your Poppea, but to be overshadowed by your Lucano (Mark Tucker) as well looks like carelessness. Hanchard is certainly not an unstylish singer, but she lacked the vocal power to make any real impact. The powerful headstrong emperor portrayed by Monteverdi's vocal writing here came across as a besotted lapdog with ineffectual teeth. Some of the vocal ensembles - the chorus of Seneca's friends, for example - were thrilling, and the EBS played with unerring panache, both in flexible and varied continuo accompaniment and in Peter Holman's convincingly reconstructed ritornelli.

Final perf: 7pm tomorrow QEH, South Bank Centre, London SE1 (071-928 800)