The Lion, The Witch and The Wardrobe, Threesixty Theatre, Kensington Gardens

Co-directors Rupert Goold and Michael Fentiman have not taken an easy option here. Given the wintry setting and the cameo from Father Christmas, The Lion, The Witch and The Wardrobe would have made a great posh panto in December. Instead this ambitious attempt at event theatre has opened in May, with London gently grilling in a heatwave. Luckily Threesixty Theatre's state-of-the-art circus-style tent stayed airily cool, although the production was a little tepid at times.

Every well-read fantasy fan must surely know the CS Lewis tale of the four frightfully English Pevensie siblings, (pictured below) evacuated during the Blitz and having an unlikely adventure in an old Professor's house. Peter (Philip Labey), Susan (Carley Bawden), Edmund (Jonny Weldon) and Lucy (Rebecca Benson) go through the clothes-filled cupboard and find themselves in Narnia, caught in the crossfire of the fight between good and evil. From the moment that Lucy disappears inside the wardrobe which rises from under the stage and then sinks back down after she is out every trick in the theatrical book is lobbed into the mix, from skilful animation on the walls to puppetry, dance and forgettable music.

Forbes Masson, who was a very entertaining Fool in Goold's King Lear is very entertaining again but a little underused as kindhearted faun Mr Tumnus who takes Lucy under his wing. As the White Witch Sally Dexter – Gertrude to Michael Sheen's Hamlet last year – plays it very straight, tempting Edmund into betrayal with Turkish Delights and the promise that he will one day rule over his siblings. One can imagine Frances Barber really getting her fangs into the role, while Tilda Swinton was an icily evil Witch in the 2005 movie. Dexter, by contrast, is a little too detached, at times appearing to be thinking about popping down to Ken High Street for some new boots.

The four young adults who play the children are uniformly good. Carley Bawden, recently seen in Pippin, is particularly persuasive as sensible Susan. And Goold's adaptation tells the story fairly faithfully. The main problem is the in-the-round setting, which should be the selling point. From theartsdesk's seats (and press tickets are usually the best seats in the house) one could not, for instance, see the children enter the wardrobe. At other times the cast inevitably had their backs to a chunk of the audience. The stage revolves, but this is really only used to give a sense of speed when various creatures are meant to be chasing through Narnia, not to give everyone a chance to have an equally good view of the action.

The Lion king Aslan, voiced by David Suchet (pre-recorded, unless Monsieur Poirot lurks under the boards every night) is tail-waggingly brilliant. A few skeletal features and some deft movement from the two puppeteers inside the frame brings the saviour of the story roaring to life. At one point as Aslan bounds along the climax to his running is almost orgasmic. He is every bit as memorable as anything in War Horse, but the thunderous sub-Satanic sacrifice scene is which he gives up his life to save Edmund is ridiculously over the top, more akin to a tabloid representation of a night on the tiles with Aleister Crowley than an allegory of Christ dying for man's sins.

This spot of pagan palaver is typical of the uneven tone of the drama. Actors inventively dressed as hooved woodland creatures – think Mighty Boosh-meets-Singing Ringing Tree – endlessly come and go. Sometimes they break into song, but not enough to call this a musical. Apart from brief scenes with Mr Tumnus and later a pair of bickering beavers there is not much light relief. Towards the end when the children take on the White Witch's army the potential for a spectacular fight slamdown, which would have appealed to all the nice middle class boys in the audience, is squandered and the combat over all too soon. The Lion, The Witch and The Wardrobe certainly feels like event theatre, but it is an event that could have been even better.

• The Lion, The Witch and The Wardrobe is at the Threesixty Theatre, Kensington Gardens, until 9 September