L'Incoronazione di Poppea, Barbican, London

"You'll come to a sticky end, lass," warns Poppea's nurse at the start of L'Incoronazione di Poppea. "Beware of kings."

"You'll come to a sticky end, lass," warns Poppea's nurse at the start of L'Incoronazione di Poppea. "Beware of kings." Nursey was right. Having seen off both mother-in-law (shipwreck) and rival (veins opened, says Tacitus), she was kicked to death (while pregnant) three years before Nero fell on his sword. Others fared no better: Seneca cut his wrists; Otho - aggrieved spouse - grabbed the purple for three months before he, too, committed suicide.

You don't get all that in the opera. Monteverdi climaxes with the rampant victory of unfettered Eros, and Poppea and Nero triumphant. There were two main heroes - composer apart - of this Barbican concert performance: the fabulous librettist, Giovanni Francesco Busenello; and René Jacobs's ensemble, Concerto Vocale - their detail was simply stunning.

Why is Busenello so hot? Scarcely born when opera was launched in Florence and Mantua, by the 1540s he was spawning libretti as good as Verdi's. His juxtaposition is astonishing: witness the outrageous, camp courting of page and serving girl, immediately after Seneca's suicide. Each time it gets nasty, there comes a joke, like the togged-up nurse's ridiculous social climbing. When Ottone, in women's clothes, tries to assassinate Poppea, the grim and the funny fuse.

This is brilliant stuff. Was it matched by what we heard? To a degree. Jacobs' continuo troupe sounded on even better form than for its prizewinning rendition of Cavalli's Eliogabalo; bits of the singing - all dramatically energised - verged on the subfusc.

Let's be clear: the best was superb. We were held spellbound - though rarely by the young central duo. Neither the Argentinian Veronica Cangemi (Poppea) nor the Ukrainian Zoryana Kushpler has quite yet arrived. Not till the fabulous final duet, "Pur to miro", did I melt.

By then, Anne Sofie von Otter had given us Ottavia's great farewell, "Addio Roma". The Swedish mezzo invariably delights. Yet even she epitomised the evening's drawback: we got the voices' drama, but what one craved - even from the Algerian soprano Amel Brahim-Djelloul's delightful Valletto or Antonio Abete's fine Seneca - was rich and glowing tone.

The evening's palpable stars were Tom Allen's dotty Arnalta, Lawrence Zazzo's love-torn Ottone and the blissfully bizarre countertenor Dominique Visse as Ottavia's nurse. I'd like to hear more, too, of the Icelandic tenor Finnur Bjarnason, who played Lucano: their "Non mori, Seneca, no" trio was a real joy.