There’s nothing new in spoofing the acting profession, and I suppose we expect digs in the rib rather than pokes in the eye in a show that mocks various playwrights – Pinter, Chekhov, Tennessee Williams and Alan Bennett to name but a few. But while the comedy duo the Black Sheep may have picked an obvious target, they hit it with plenty of joyful thwacks. This is the funniest thesp-fest since Christopher Douglas and Nigel Planer created mock-luvvie Nicholas Craig for their 1988 book I, An Actor.

But I, Lear (coincidence, or homage?) is sustained as much by the fizz of its clowning as by the sharpness of its satire. Andrew Jones and Ciaran Murtagh play overwrought old-timer Hugh Carpenter and cavalier smoothie Chester Bleinheim, two rep throwbacks who are here to masterclass us in the ways of the stage. Murtagh upstages Jones as they goon around in Greek masks and he drags up to play a Williams heroine; Jones scores a hit with his Bennett drone – with its spot-on talk of “Warburtons barn cakes” – and they both merrily debase themselves for the Cats routine and a King Lear finale that brilliantly reincorporates their earlier sketches.

If it doesn’t numb the critical faculty throughout its 70 minutes, that’s because Jones and Murtagh don’t have quite enough of an angle to keep the spoofing surprising. Tensions are hinted at, not developed. Murtagh delivers a Charles Dickens monologue with brio, but why pick Dickens, Sherlock Holmes and Bennett’s television work in a show that’s ribbing theatre?

I, Lear, which has already done well in Edinburgh, has a true Fringe show’s mix of brilliant moments and flat patches. But the director and co-writer Cal McCrystal, the comedy world’s Mr Fixit for this kind of graduate tomfoolery, ensures that there’s tight thinking behind the apparent free-for-all. Its broad, contagious sense of fun is sustained by a respect for the audience’s intelligence. So while I, Lear has nothing huge to say about its subject-matter, it also offers enough belly laughs to send you out happily into the night.

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