Knockout Week continues as the remaining 11 contestants are split into two groups and get their first taste of professional cooking when they have to run an entire lunchtime service on their own. In this episode, the first group head to Typing Room, a London restaurant over seen by Lee Westcott, a protégé of Jason Atherton and Rene Redzepi's Noma. During a busy service, the five amateurs are responsible for serving up every dish on the menu to paying customers. Who will falter as they cook in a completely unfamiliar and demanding environment? 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 a dish from scratch that looks and tastes exceptional. They can choose from a plentiful array of seasonal produce that ranges from the everyday to top-end ingredients. 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 - renowned Professional MasterChef judge and formidable perfectionist Monica Galetti. After this, one of them will be going home. Who will crumble under the pressure and who will make it through to Friday's challenge - the gateway to this year's semi-finals? In a competition where only the food matters, these amateurs will need to stand out to survive - taking another precious step towards being crowned MasterChef Champion 2015.