5/13 The four contestants tackle a royal-themed Invention Challenge.
4/13 The four contestants tackle an animal-themed Invention Challenge.
3/13 The four contestants create cakes to celebrate their favourite festivals.
2/13 The four bakers make tricky jammy shortbread biscuits and a chocolate celebration cake.
1/13 The four hopefuls must wow the judges with their own amazing 'cakes from outer space'.