The spotlight is on Santa this week on Róisín Meets. Mathematician Hannah Fry explains The Indisputable Existence of Santa Claus, while Róisín's daughters Joya & Priya report back on their trip to meet the man in the red suit at home in Lapland. And, as if that wasn't enough, we also have a festive ditty from Paddy Casey to get you in the mood for Christmas.