"What's the point of A Christmas Carol without any Muppets in it?" asked a friend when I told her that I'd be reviewing Jack Thorne's new adaptation of this most beloved of Dickens stories. Just because something has been adapted before doesn't mean it isn't worth revisiting, of course – especially when it comes to Christmas shows – but if you're going to tackle an old favourite, you need a good reason to do so. Watching Matthew Warchus's production, starring the inimitable Rhys Ifans, I couldn't for the life of me work out what that was.

The show is full of charming festive touches. A trio playing violin, cello and accordion set the scene as we take our seats, while becloaked and top-hatted actors proffer mince pies. Music is one of the strongest elements of the production, Christopher Nightingale's arrangements of Christmas carols providing a beautiful underscore, sung by the cast and performed by Martin Robertson, Steve Bentley-Klein and Justin Pearson and musical director Will Stuart. Rob Howell keeps things simple design-wise, evoking the bleakness and parsimony of moneylender Ebenezer Scrooge's world with empty door frames, dark wooden boxes and flickering lanterns.

The company tell the story of Scrooge's encounters with the Ghosts of Christmas Past, Present and Future using Dickens' own words for the most part. They're good words, no doubt about it, but all this narration makes for a rather flat experience – the theatrical equivalent of a supermarket mince pie. Where the play comes to life is in the scenes without narration, in particular where Rhys Ifans' Scrooge finds himself face-to-face with characters from his past, his belligerence about learning the lessons the Ghosts are trying to teach him belying the seamlessness with which he slips back into old roles.

Ifans brings an impressive depth to Scrooge, drawing on a difficult relationship with an indebted, drunken father invented by Thorne as a way of explaining the origins of Scrooge's ambition and greed. Other characters fare less well in the three-dimensionality stakes, but the cast do their best in the circumstances.

Just as you think the evening is wrapping up, Scrooge having pledged to leave his bah humbug days behind him, the production undergoes a radical change of pace and flavour. The fourth wall-smashing silliness that takes over at this point bears almost no relation to what has come before, and the ending is mawkish in the extreme (not a surprise given that it's Dickens we're watching), but it's all such fun that it's impossible not to go along for the ride. You'd have to be a muppet not to walk out with a smile on your face.

A Christmas Carol runs at the Old Vic until 20 January.

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