From the start, the already cluttered set, with its pair of underground railway arches, its train track and station sign for Sloane Square, made it clear, at least to the adult section of the audience, that this Peter Pan was going to delve deeper into the dark psychological substructure of J.M. Barrie’s creation than is usual for a children’s opera. Peter Llewellyn-Davies, one of the five brothers who served as models for Barrie’s Peter, threw himself under a train at Sloane Square at the age of 63; two of his brothers had died in their early twenties, one in the trenches and the other in a drowning accident which may have been a double suicide with a friend. Richard Ayres’s Peter Pan begins with Mr and Mrs Darling superintending the building of their house. Afterwards, Mr Darling takes the train to his work in the City, while Mrs Darling and Nana the Newfoundland nurse put the unruly children, John, Michael and Wendy, to bed. Their room is filled with furniture, alphabet blocks and a huge ticking grandfather clock which, of course, is to end up transformed into the fatal crocodile.

Musically, the opening of the opera is lively and energetic in its scoring, but the orchestration tends to veil the voices and I was frequently forced to look up at the surtitle screen (the English, not the Welsh one) to check what the singers were saying. The strings and brass pound away in a manner somewhere between Janàček and Martinů for most of the riotous action scenes, while melting into more lyrical woodwind writing whenever a moment of calm descends. Ashley Holland was clear and funny as Mr Darling, with enough of a hint of violence and temper to make it clear that he was the villain of the piece. Hilary Summers made a lyrical and loving Mrs Darling, although her aria about tidying up the children’s thoughts for the night, sweetly voiced, was a touch on the sugary side. Lavinia Greenlaw, the librettist, is a distinguished poet and dramatist, but there were moments when her use of stammered, broken-up lines and copious repetition muddled, rather than clarified, the storyline, not working as well with the music as it should have done.

Peter Pan’s arrival put the show on a whole new level, quite literally, as the countertenor Iestyn Morris had to work just as hard as his aerobatics as he did at singing his technically taxing lines, which occasionally dipped his voice down into a growly baritone which made the casting of a countertenor seem even creepier. For more than a century, the stage Peter Pan has been cast as a woman, and although the cinema has familiarised us with pre-pubescent Peters like Jeremy Sumpter, finding a countertenor singing the role comes as a shock, in a way that casting a boy treble (musically impossible though this might be) would not. Morris’ brilliance in his flying harness, as he swooped across the bedroom, walked up the walls and somersaulted in the night sky was a high point of the show.

With the children transported to Neverland, and Mr Darling in the doghouse, Act II opened with some vigorous work from the WNO Chorus as the Lost Boys, followed by their reappearance as pirates and Native American squaws (that’s what the synopsis calls them, using a neologism that seems anachronistic) who are respectively led by Holland as Captain Hook and Summers as Tiger Lily. Tinkerbell remains a projection, signalled by sparkles of light and twittering percussion and strings. Her death and resurrection, brought about by Peter calling for some noise from orchestra and audience (willingly provided by a large number of children on £1 tickets, an excellent marketing idea), was as sentimental as it is in the play. I’m still not sure if I believe in fairies.

Holland excelled as Hook, with full-bottomed wig, hat, hook and curly moustaches, and his machinations to kill the Lost Boys and capture Wendy are fought off by Tiger Lily, Peter and the Darling children. Hook’s ship is Mr Darling’s railway carriage transformed, and other domestic transformations show that we are really in the children’s bedroom all along. Most spectacularly of all, the crocodile (clock-o’-dial?) turns out to be the grandfather clock with a long scaly tail and snapping jaws, who rudely poops the ticking clock, and remains there after a silent, deadly menace.

There is menace in the music, as there should be, and some rattlingly effective scoring during the fight scenes. However, overall it seemed to fall into an unsatisfactory territory between musical and full-blown opera, and the two acts, each well under an hour in length, did not allow the story sufficient room to develop. Ran Arthur Braun directed both flight and fight, and did a wonderful job considering that the stage itself was impossibly encumbered with objects (especially the alphabet blocks) which never spelt anything special, and blocked the view on several crucial occasions.

The visionary world evaporates, the children fly home to find Mrs Darling sobbing in their bedroom, and Mr Darling still in the doghouse. Peter does not join them in their reunion (although Tinkerbell makes sure that the Lost Boys do) but ends up at Sloane Square Station, gazing longingly at the train tracks. I ended up feeling that the innocence lost in the translation from Barrie’s play to Ayres’s opera was not replaced by anything musically or dramatically worthwhile, and that much of the childlike subtlety of the play’s imaginative world had been exchanged for an ineffectual knowingness that added nothing of value.