Britain at Low Tide

Tori explores an 18th-century shipwreck and discovers a prehistoric well shaft. Plus: the harbour that took 63 years to build but only worked for four months.

In Dorset, Tori and the team reveal the story of the world's first aircraft carriers. They also discover how this coastline played a vital role in D-Day and search for a unique and huge Iron Age monument that can only be seen - sometimes - for a few hours a year.

Tori examines various attempts to make the River Clyde deeper to get ships into the heart of Glasgow, and investigates the role of an odd-shaped vessel in a boat graveyard

In this episode Tori visits the Severn Estuary and investigates a mysterious medieval ruin on a bleak island. Who built it, and why? Could it have been a religious site? Was it an early lighthouse or beacon? Further along the coast she visits the site of the medieval village of Sudbrook, which simply disappeared into the sea. She finds out how important the ferry crossing at Aust was during the 20th century and is shown a photo of a famous passenger who used it: Bob Dylan. And she investigates the story behind the very first attempt to build a tunnel underneath the Severn. At the moment, all this archaeology is available to anyone who cares to go looking for it, but rising sea levels and coastal erosion mean it won't be very long before it's all swept away. Britain at Low Tide captures a vanishing past for us all to see.

In East Yorkshire, Tori uncovers the story behind a dramatic night when a fishing trawler went wildly off course in the North Sea. The massive remains of a World War I fort lead Tori to tales of love in a Yorkshire village. And she learns the strange fate of two ships that were built in Hull but ended up on top of a mountain in Peru.

In Fife, Tori explores a wreck near the scene of one of Britain's worst ever railway disasters and examines stone carvings left in caves by one of Scotland's oldest tribes.