A place in the quarter-final is at stake, and this week the sewers must face three technically-taxing challenges from the world of lingerie.

First up, in the Pattern Challenge, it is time for bed as the sewers are asked to make a pyjama blouse. Piping is an intricate undertaking, and it should cover the cuffs and front.

For the Transformation Challenge, the sewers take shapewear and lace and, using their unique structure and form, create new outfits.

Finally, it's ‘boom or bustier' as the sewers tackle boning and make bustier dresses in the Made-to-Measure. Their ability to fit a model is put to the test - there is nowhere to hide if a bustier dress is not fitted well.

Kiell Smith-Bynoe welcomes the four semi-finalists into the sewing room as the judges set three challenges inspired by design icons.

First up, master pattern cutter Cristobal Balenciaga is the inspiration for the Pattern Challenge, as the sewers recreate a version of one of his dresses.

In the Transformation Challenge, taking the lead from the iconic Jean Paul Gaultier, the sewers are given a pile of neck ties and tasked with using them to create a brand new garment.

Finally, in the Made to Measure, Coco Chanel is in the spotlight as the sewers get the chance to scour her long career to find a style to make an outfit inspired by her work.

Four remaining sewers, three challenges, but one will miss out on a place in the final.