This year's first quarter-final sees the strongest four chefs from the first two heats return to face two more demanding challenges.The first is an Invention Test, where the chefs must create an outstanding dish using preserved and tinned food. They have ten minutes to select their ingredients before designing and executing a dish in just one hour. Are these professionals able to dig deep and think on their feet to elevate a dish of tinned beans and pressed ham to restaurant standards?For their second challenge the contenders must cook for three of the UK's most discerning restaurant critics: Jimi Famurewa, William Sitwell and Tracey Macleod. They have one hour and 15 minutes to prepare a two-course meal. Can they thrill as well as serve on time to remain in the competition, or under the stress will they overpromise and underdeliver?Only the two most talented chefs will go through to the semi-finals and continue their pursuit of the 2021 title.