Take a liberal helping of Ayckbourn, add a sprinkling of Sondheimesque songs, stir well with a cupful of Joe Orton, and what do you get? A unique show which pulls the rug from under anyone who still thinks that Christmas Day should be a perfect occasion.The horrors of family Christmases are all here in quantities that would fill even Santas boots: Mum compulsively adjusting the cushions and filling up the nut bowls, Dad entrenched in front of the television watching endless repeats, presents that havent been wrapped, the smell of burning from the kitchen, the son bringing his new girlfriend home for parental approval, inevitable rows and arguments... What makes this Christmas different is that their lonely, unfit and emotionally retarded banker son Anthony (Rob Hughes gives the only performance this side of the next decade which will make you feel sorry for a banker) has brought a high-class escort home to masquerade as said girlfriend. Not for sex as you might imagine, but so that Christmas Day can be that fantasy occasion he has never experienced - a real family Christmas with, for the first time in his life, a girl on his arm. Last Christmas, they brought me Brokeback Mountain as a present he quips. As Serbian escort Irina, Erica Guyatt is a hoot, arm-candy so hard you could break your teeth on her. As she says (and sings) Im good at what I do. The only trouble is, her fee is minus expenses. When the not-so-fantasy Christmas presents emerge, Anthony realises just how much his perfect family Christmas will cost.Jessica Martin and Andrew C. Wadsworth are pitch-perfect as the suburban parents, dancing dutiful attendance on their son and the new lady in his life. Mum isnt so sure she is quite right for her darling boy, but Dad is too infatuated to complain. Three quarters of the way in the comedy gets shunted abruptly aside and this small scale musical takes a big, blacker and bleaker turn. Its not just the tantrums over the burnt gingerbread, or the fact that Dad has hidden the DVD of Its a Wonderful Life that bring the day to a crisis. Its a far deeper issue. The superb twist brought gasps from the audience on the night I was there, and rightly so. This is an extremely clever piece of writing by Kate Darby, and Luke Batemans lovely, simple score only serves to underpin the complex tragedy beneath. Its a wonderful life? Forget it. This is a wonderful play.