4x5 - The Great British Bake Off

Almost halfway through the Bake Off and the remaining eight bakers are faced with biscuits and traybakes. First up, a Signature Challenge that requires them to do something apparently simple - produce their favourite traybake. The bakers offer Mary Berry and Paul Hollywood their twists on everything from bakewells to banoffees and brownies. Next they face the thinnest Technical Challenge ever devised on Bake Off - the French classic tuiles, biscuits formed into fragile rolls and decorated with delicate designs of piped chocolate. And finally, a Showstopper of epic proportions as the bakers make 'biscuit towers'. Mel and Sue follow the trail of biscuit crumbs as the bakers produce architectural feats inspired by everything from ancient Japanese civilization to one of time travel's most feared enemies. Meanwhile, we discover how the Tottenham Cake, a pink, iced traybake produced by the Quakers of North London, became a match day treat at White Hart Lane.