THE S4C history series Darn Bach o Hanes on Monday (9 pm, English subtitles available) goes in search of medieval tunnels of the harbour town of Tenby.

Presenter Dewi Prysor follows the network of medieval tunnels that lie underneath the current Georgian buildings of the historic seaside town.

"Apart from the Norman walls and castle that were built to keep out Welsh forces, the only medieval buildings left are a striking Tudor house, which is now run as a museum by The National Trust, and the ancient St. Mary's Church. But underneath the town, there is a labyrinth of fascinating tunnels," explains Dewi.

With the help of local historian John Beynon and manager of the Hafod y Môr holiday accomodation, Heledd ap Gwynfor, he traces a network of tunnels which apparently linked the property of local merchant and ship-owner Thomas White to the harbour.

John Beynon explained: "Behind Boots the chemist, there is a door that leads to a chamber where Tudor merchants would stock wine, coal and other provisions.

"It also forms part of a network of tunnels that lead to the harbour. It is said that Henry Tudor and his uncle Jasper hid there from the soldiers of the then English king, Richard III, but this may well be a myth."

Also, in the programme, Dewi explains how the small Ceredigion village of Plwmp got its name, Gwennan Schiavone looks at the collection of papers bequeathed to The National Library of Wales by Breton Nazi collaborator Louis Feutren, and Rhodri Llwyd Morgan looks at the records of meteorites that have landed in Wales.