A place in the quarter-final is at stake this week, and the challenges are all about lingerie. Host Sara Pascoe starts the sewers off with a fiddly pattern for a lace underwired bra and matching knicker set. With such small pattern pieces, there is no margin for error, and Patrick and Esme's eagle eyes will spot every mistake.

The Transformation Challenge requires the sewers to take thermal underwear and turn it into daywear. Then male models fill the sewing room to be fitted for a pair of luxury pyjamas. One sewer wins Garment of the Week and another is asked to leave the Sewing Room.

Sara Pascoe welcomes the four semi-finalists into the Sewing Room to celebrate the influences of Japanese design and sewing. For the Pattern Challenge, Esme has collaborated with a Japanese designer to come up with a kimono-inspired dress that proves to be a brain-teaser. This is for a place in the final, after all.

The Transformation Challenge is on a smaller scale than usual, as the sewers take worn-out denim and apply the Japanese techniques of sashiko and boro to mend areas of wear and tear, enhancing it with appliqué and embroidery.

Finally, their Made to Measure challenge is to fit an outfit to their model which has elements of origami folds and pleats.