Toulouse to Carcassonne

S1, E3: David's cycling mettle is put to the test as he and Hugh travel along the Canal du Midi and tackle some of the most challenging parts of the route so far - but will David's dodgy knee hold up? Along the way, Hugh and David visit an artisanal dye expert who reveals the ancient magic behind turning things blue. At the Seuil de Naurouze they gate-crash a rather unusual local fiesta, and then they dine in Castelnaudary - the cassoulet capital of the world - so Hugh can sample his favourite French dish.