Ion, Linbury Studio Theatre, Royal Opera House, London

Param Vir's supremely lucid and musically appealing Ion has been a long time in the making. After this summer's dismal offerings of the Genesis Opera Project in collaboration with Aldeburgh Almeida Opera, here, at last, is a piece worthy of the description "opera".

Ironically, Vir's piece was commissioned by the same "backers": in 2000, it received a concert performance at the Aldeburgh Festival. Now, London has just seen the UK premiere of the fully-fledged staged work - but nine performances had already taken place, a result of co-production with Opéra National du Rhin in Strasbourg and Berlin Festival, plus performances in Mulhouse and Colmar.

The fluency of the performance was palpable, even if European touring has meant three different orchestras. The indefatigable Michael Rafferty - music director of the astonishingly versatile Music Theatre Wales responsible for this show - seems seamlessly to have moved from one band to another. Euripides' Ion makes a great operatic book. Vir came across it in translation by David Lan - known for his prize-winning TV drama documentaries and work with the RSC - and it was with him that he worked on clarifying the text and adapting it to musical form.

Ion is a myth for our times, although messing with Greek gods invariably produces twists: a barren couple, Creusa and Xuthus, seek advice from Apollo individually, only for Xuthus to be told that the first person he sees will be his son. The wife feels thwarted - wasn't it really her shame? - so she vows to kill the "imposed" son. But then she has a secret: she was a single mother impregnated by none other than Apollo and thought that she had left the child out to die. But the child did not die, rather it became the caretaker of Apollo's Delphic shrine - none other than Ion, the first person Xuthus encounters.

Creusa's plot to poison Ion goes wrong - the wine, instead of being drunk, is thrown on the ground for a hapless dove to take a nip and expire - so Creusa, herself, is condemned to die. But the Pythia, a matronly figure who tends the oracle, reveals that in her possession is a basket in which she found a child. Recognition and joy all round.

Michael Bennett was a touching Ion, if occasionally pressing the voice too hard; Rita Cullis and Graeme Danby a believable middle-aged couple; Gwion Thomas a supremely musical Hermes (and Servant); Nuala Willis sonorous as the Pythia; and Louise Walsh, the (somewhat unlikely) coloratura Athene. Michael McCarthy's production was affecting and stately, Ace McCarron magically lighting Simon Banham's design. A triumph.

On tour: Anvil, Basingstoke (01256 844244), 4 Nov; Lighthouse, Poole (01202 685222), 9 Nov; Lyceum, Sheffield (0114 249600), 13 Nov; Clwyd Theatre, Mold (0845 3303565), 16 Nov; Lawrence Batley Theatre, Huddersfield (01484 430528), 29 Nov; New Theatre, Cardiff (029 2087 8889), 30 Nov; CBSO Centre, Birmingham (0121-767 4050), 9 Dec