Derek gets wet from rain, an overturned kayak in the sea and a hot tub with a view! Walking the Pembrokeshire coast from Newport to Fishguard, the weatherman also learns how the last invasion of Britain was foiled by a feisty woman. Archaeologist Dr Erin Lloyd Jones explores the link between Stonehenge and the Preseli mountains, and party planner Onkar Singh Purewal visits a "Hansel and Gretel" house covered in shells.