Claudia Winkleman presents the semi-final. The four amateur sewers return to compete in three more challenges. Savile Row's Patrick Grant and sewing teacher May Martin set them a pattern for a child's dress which tests their ability to follow couture techniques on a miniature scale. In the alteration challenge they are asked to tailor a dress with precision and they create a made-to-measure jacket which must fit their model perfectly, after which one of them is asked to leave the Sewing Bee.