Sam and Mark host, and judges Allegra McEvedy and Graham Hornigold set four wannabe bakers - Grainne, Isaac, Matilda and Will - two more challenges. Their baking knowledge is tested with a surprise recipe for a chequerboard biscuit. The challenge requires mathematical precision to avoid falling foul of ruler-wielding stickler for accuracy, Graham. Next, the bakers produce their own versions of a show-stopping vegetable cake. Beetroot, parsnip, carrot, runner beans - anything goes! As long as it's delicious, because a place in the quarter-finals is up for grabs. Show less