Prue Leith set this challenge. Le Gateau Vert is reputed to have been Claude Monet's favourite treat. The bakers needed to make a light pistachio genoise sponge, sandwiched with a pistachio crème au beurre and covered in a fondant coloured green with spinach.

Prue Leith: "The most common problem with the genoise is not getting the volume of air into the cake. This cake needs to be sliced into three layers, so it must be at least an inch and a half tall before cutting. It also needs to be light and delicious."

Paul Hollywood: (tastes) "Oh, that's beautiful. This is about the basics being done well and I think it's a fantastic challenge."

Prue Leith: "The person who keeps their head will do the best, because there is a real risk of panicking when you see how much you've got to do."