Our third Christmas Cracker! Seeing a performance of Tchaikovsky’s ballet, The Nutcracker, is, for many people, as much a part of Christmas as tinsel, turkey and a tree. It premiered 120 years ago yesterday, in the Mariinsky Theatre in St. Petersburg. As productions around the country get under way this year, Sugar Plum Fairy Sarah Lamb, and conductor Koen Kessels, both from this Christmas’s Royal Ballet production of The Nutcracker, and Judith Mackrell, The Guardian’s dance critic, share their thoughts on what gives Tchaikovsky’s exquisite confection its enduring appeal.