Agrippina was a force to be reckoned with: the granddaughter, sister, niece, wife and mother of four Roman Emperors (and lover, incestuously, of at least two). As Mary Beard points out in her brilliant programme introduction, "Agrippina was probably the best connected woman that the Roman world ever saw" – and one of the most ruthless. Her absolute determination to reach her goal (of making her son, Nero, Emperor) is rivalled only by her cleverness in pursuing it; and by her callousness in attaining it. Agrippina shows us a woman who will stop at nothing; ignoring omens (very dangerous in the ancient world) to force through her vision of the future, never flinching in the face of danger, always ready to adapt her plans – even mid-aria – to win. This joyous production by English Touring Opera beginning its tour at the Royal College of Music's Britten Theatre, directed by James Conway on a beautiful revolving set by Samal Blak, makes the most of the music, the characters, and the alternately hilarious and unsettling plot of Handel's early masterpiece.

The Old Street Band makes a gorgeous sound under the baton of Jonathan Peter Kenny. One of the delights of Handel's Agrippina is the sometimes sarcastic contrast between the tone of his music and the content of Grimani's libretto, which James Conway has translated into witty and well-constructed English. In an interesting move, the surtitle screens show only captions for scenes: "In which Poppea expresses herself horticulturally" being my favourite... We were also treated to background information on the plot during the overture via these screens: a nice touch.

In linear terms, Agrippina is a prequel to another of English Touring Opera's offerings for this tour, Monteverdi's The Coronation of Poppea. Certain singers perform in both operas, with Paula Sides playing Poppea in each, while Jake Arditti transforms from Amor into a marvellously peacock-strutting Nero for Agrippina and Nicholas Merryweather takes a larger role in the Handel as the devious, yet duped Pallante. It is particularly exciting to be able see these singers in two connected roles in a short space of time; you get a much better idea of their depth and range, and it is a real test of their acting – which they all pass with flying colours.

Paula Sides portrays each Poppea with a generosity which brings them both to life, but also with an intelligent distinction between the two. Her Handel Poppea is virtuous, tender, and loving, though not beyond spiteful revenge when she feels she has been scorned by Ottone or hoodwinked by Agrippina; her Monteverdi Poppea is a self-absorbed sensualist with an eye to the main chance, no redeeming features beyond beauty, and a tyrant's disregard for anyone in her way. In each role, Sides' superb voice (and brilliant acting) delights, and in Agrippina her rose-cutting aria was a revelation.

It was great to see Nicholas Merryweather in a larger role, which he took on with relish and executed with panache; his voice seemed perfectly suited to the music, he simmered with lust and self-interest, and his scenes alone with Agrippina (Gillian Webster) really unleashed his acting. This is someone who needs to be in the foreground, not the background. Jake Arditti once again astonished us with the range, clarity, power and energy of his performance; his voice is breathtaking. He seemed a little nervous at first, but it soon became clear that he was showing us Nero's transition from fragile, spoilt boy to madly indulged, frighteningly arrogant man; and the seeds of madness (and shadows of incest) were cleverly and delicately implied. The aria in which he renounces love (on his mother's orders) is particularly fabulous.

Gillian Webster is a brilliant Agrippina: strong, fierce, and indefinably charming. There is something unstoppable in her performance which makes her loveable, even at her most threatening; an engaging, conspiratorial naughtiness which reminded me oddly, but irresistibly, of Margaret Rutherford. She openly exults and connives with the audience in her schemes, and as she becomes more deadly, we simply admire her more. Her solo aria, "Foreboding", inventive, sculptural, and haunting, was my personal musical highlight. Andrew Slater was a wonderfully louche Claudius, who rolled into each scene as if he had just slid off Keith Allen's houseboat after a particularly wild party; his portrayal of misplaced middle-aged lust was a brilliant mixture of befuddled adoration and pathetic self-delusion, but behind it conveying very real sense of the extent – and threat – of Claudius' power. Luke D. Williams, as Claudius' servant Lesbo, had quite the best costume I have ever seen on a stage anywhere, and sang, pouted and minced with foppish grace. Russell Harcourt was a despicably, delightfully weedy Narciso, and Clint van der Linde a romantic, loveable Ottone, whose "I shall go" had me humming all the way home.

Agrippina is an opera of balance and tension. It reverberates with memorable characters, yet relies on a layer of artificiality. It has moments of real humour, sophistication and elegance, yet examines the most basic human instincts with a coldly cynical eye. Its arias bloom in lovely, almost impossibly complex phrases; then a chorus, "This day of rejoicing", taut as the drum which underpins it, crackles with focused energy. For an evening of variety, excitement, intrigue, humour, and death-defying singing – you need look no further.

Handel: Agrippina, at RCM, Britten TheatreCharlotte Valori reviews English Touring Opera's production of Handel's Agrippina, at the Britten Theatre, RCM, before touring nationally.5