It's the semi-final, and the four remaining bakers must set to work on producing 24 exquisite choux buns. Prue Leith has set a complex technical for her first semi-final that leaves everyone stumped. And there's a meringue sculpture showstopper where the bakers mustn't crack under pressure. Noel Fielding and Sandi Toksvig present, while Paul Hollywood passes judgement alongside Prue.