oe Lycett hosts the semi-final, as the four remaining sewers go back in time to the 1940s. Attempting to revive both the glamorous and thrifty styles of the decade, they tackle its most elegant and innovative garments.First up, judges Patrick Grant and Esme Young challenge the sewers to make the decade's most famous trousers, Oxford bags, perfect for dancing the jitterbug and swing, but tricky to make. Creating the perfect trouser involves grappling with oversized pattern pieces, fly zips and a waistband with pleats to make room for the extra-wide legs.For the Transformation Challenge, it's time to take a leap of faith, as the sewers are set a wartime task to turn old parachutes into glamorous dresses.In the Made to Measure challenge, the sewers take on their final icon of 1940s fashion, Dior's New Look. Characterised by an hourglass silhouette and involving masses of fabric, this style means each sewer must exaggerate their model's figure to create the iconic shape. Who will sew their way to victory and win Garment of the Week, and for whom will 40s week signal the end of an era, as they become the ninth sewer to wave goodbye to the Great British Sewing Bee?