Knockout Week continues, with the eleven remaining contestants facing a baptism of fire as they are split into two groups and tasked with running a professional lunchtime service on their own. In this episode, the first group heads to a London restaurant headed up by award-winning chef Stevie Parle. During a busy service, the five amateurs are responsible for serving up every dish on the menu to paying customers. Then it's back to MasterChef HQ for an Invention Test to show John and Gregg just what they have learnt. In a last-chance bid to stay in this year's competition, each contestant has to show they can invent an exceptional dish that is worthy of gracing the table of a professional restaurant. In an unexpected twist, the contestants discover that they not only have to present their food to John and Gregg, but also a guest judge who will be helping John and Gregg evaluate the five amateurs - the formidable Professional MasterChef judge, two Michelin-starred Marcus Wareing.