Neil Oliver explores the province of Finistère, "The End of the Earth", and meets a lighthouse keeper made famous by one of the world's most reproduced photographs. Nick Crane joins the "Onion Johnnies", who gave us our stereotypical image of a Frenchman, complete with stripy tee shirt, beret and bicycle laden with onions. Alice Roberts reveals the life saving chemical element that's locked away inside seaweed and Miranda Krestovnikoff dives for a seafood delicacy. At Carnac, Mark Horton wanders amongst the mysterious lines of standing stones, erected thousands of years before Stonehenge, to investigate their age old connection with Britain.

• Alice Roberts
• Miranda Krestovnikoff