Overview: It’s the third quarter-final, and the four best chefs from this week's heats face two more demanding challenges. First is an invention test. The dish they create must be centred around the use of citrus, and the judges will want to see that the chefs can handle variety and execute a dish spontaneously and with zest. Then the chefs will cook for two of the UK’s most discerning restaurant critics, Jay Rayner and Tracy MacLeod. Only the two most talented chefs will go through to the semi-finals.