It's the grand final and Guz Khan, Sophie Willan and Ivo Graham return to help the Tiny Big Brains take on a colourful chemistry conundrum and a shocking logic puzzle.

The Tiny Big Brains are paired with Guz Khan, Maisie Adam and Phil Wang to tackle a tambourine-playing physics puzzle and a frustrating logic game separating soft-toy Jack Dees.

The Tiny Big Brains are matched with a comedic partner - Tim Vine, Fatiha El-Ghorri and Ivo Graham - to complete a fruit-based periodic table problem and a dingbat country contest.

The junior geniuses direct their comedy teammates - Johnny Vegas, Sophie Willan and Lucy Beaumont - through a dog-wrangling logic puzzle and a vacuum cleaner-based maths conundrum.