Holly Willoughby and Lee Mack present as eight celebrities undertake a series of sub-zero challenges designed to test them to their limits, both physically and mentally. They are being trained by extreme athlete Wim Hof, the man who once ran a half-marathon barefoot above the Arctic Circle, and climbed Mount Kilimanjaro in just his shorts and shoes. Those taking part are West End star Alfie Boe, singer and footballer Chelcee Grimes, Strictly professional Dianne Buswell, sports presenter Gabby Logan, weatherman and drummer Owain Wyn Evans, French footballer-turned-coach Patrice Evra, rapper Professor Green and actress Tamzin Outhwaite.