David Baddiel tries to understand crying: why does water come out of our eyes when we get emotional? David sets off to meet two experts who have each studied this. They have lots of theories, but is there an answer? Producer: Giles Edwards

David Baddiel tries to understand global trade. With trade in the headlines - from both Brexit and President Trump - David is keen to understand how world trade works (or doesn't), and where the World Trade Organisation fits in. With help from Dr. Meredith Crowley, an expert in international trade and trade policy at Cambridge University, and Chris Southworth, Director General at the International Chamber of Commerce, can David get to grips with it all in just 14 minutes? Producer: Giles Edwards

David Baddiel tries to understand how the fashion industry works: what makes things fashionable? David is challenged by a listener from Wigan to explain why, when he needed to attend a family party a few years ago, the only trousers available to buy then were pleated. This sets David off on an unlikely quest to Paris Fashion Week to find the answer. When he arrives, he finds himself on the front row of a fashion show, bumps into fashion designers in the street, and is taken under the wing of one of fashion's most influential bloggers. But what is the answer, and can he explain it? Producer: Giles Edwards

David Baddiel tries to understand TV broadcasting. In the last episode of the current series, David helps broadcaster Danny Baker understand TV broadcasting. Both of them have spent decades in and around TV, but neither quite understands how it works. Danny wonders if there is a 'magic room' where all the programmes get lined up and broadcast out, and David sets off to find it. Producer: Giles Edwards.

David Baddiel tries to understand the United Kingdom's constitution. What does a constitution do? Does not having a written constitution mean we don't really have a constitution at all? Should we? And where does the Royal Family fit in? David speaks to Lord Lisvane, a former Clerk of the House of Commons, and to Lord Turnbull, once the country's top civil servant, to understand these and other puzzling questions about the constitution. Producer: Giles Edwards.