It's week three, and the heat in the kitchen is already too much for some, as the remaining 11 bakers get ready to deal with desserts. Mary and Paul are upping the ante. Having survived cake and bread, this is the first week we see the bakers having to multi-task across several different baking skills at the same time; a signature trifle combining biscuit, cake, jelly or custard in perfectly distinct layers; a technically difficult task of making floating islands, which result in various forms of unrecognisable landmass by the end of the bake and a showstopper that pulls out all the stops, getting the bakers to juggle 24 petit fours that the judges might finally deem acceptable. They are taking no prisoners, and for the first time ever, there's a baking burglary in the Bake Off tent and it becomes a crime scene. Mel explores the origins of the trifle and discovers how it was transformed in the Georgian era from an elitist dessert for the aristocracy to a dish that was accessible to the masses.

• Sandi Toksvig
• Noel Fielding
• Mel Giedroyc