Just found this online. FLOWERS!! How dare you not mention the Lucas moment from the final paragraph, young lady?!
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Richard appeared in the first of the plays, The Third Wish, written by Stephen Beresford and directed by Charlie Westenra. Like most of the other plays, it was a comedy and the cast also included Miranda Raison (his former co-star from Spooks), Niamh Cusack and Debbie Chazen. He played Dennis, the husband in a couple who'd inadvertently bought a magic Christmas tree (a miniature tree that had been brought along by one of the participants the previous evening.) As Debbie, his wife, explained to her two sisters, she'd happened to say that she wished their flat was bigger, and it had suddenly transformed into a spacious apartment (a neat way of explaining the set - all of the plays were performed on the Act 3 set of Noel Coward's Design for Living, which is currently playing at the Old Vic during the week. It depicts a luxurious New York City penthouse in the 1930s.)
She explained that Dennis (off-stage) had made the second wish, and she wanted advice from her sisters about what the third wish should be. The overweight and balding Dennis had wished to look like Richard Armitage. Which he did...
Delighting in his new body, he spent the next few minutes bounding around the stage - waltzing around the room and up the stairs with his wife, sliding down the banisters, tossing his hair in all directions (just because he now had hair to toss), crouching down with gun in hand in imitation of Lucas North... and then discovering his pecs. Like all the plays, it was hugely enjoyable and very well-received.