It's the semi-final with just four sewers left to battle it out to for a place in the final. All that stands in the way are three challenges designed by judges, Patrick Grant and Esme Young. This week they want to test the sewers' knowledge of complex patterns and pattern cutting. For the Pattern Challenge, the sewers are tasked with making an asymmetric yoked skirt inspired by modern Japanese pattern cutting.

• Claudia Winkleman
• May Martin
• Patrick Grant