Professor Heinz Wolff assigns the red, blue and green teams the task of constructing a tea-making device from humble household materials. Professor Ian Fells helps to judge the Wallace and Gromit-style contraptions. Meanwhile, presenter Lesley Judd looks at the Incredible Egg Machine. Lesley Judd, who presented the Incredible Egg Machine interludes, is perhaps best known for hosting 'Blue Peter' between 1972 and 1979. Her recollections of the show include Abba making a guest appearance and golden retriever Goldie eating a teddy bear's head. One of her strongest memories, however, is interviewing Anne Frank's father, Otto. After Judd left 'Blue Peter', she worked for a variety of programmes, including Radio 4's 'Woman's Hour' and 'The Great Egg Race'.

• Johnny Ball
• Brian Cant
• Lesley Judd