First of a six-part documentary series presented by Dan Jones exploring the history and legends of the UK's great fortresses. The first episode takes Dan behind the battlements of Dover Castle, where he descends into an underground lair to discover how a vast network of tunnels has been used to defend both the castle and the country for centuries.

Built by William the Conqueror, the Tower of London has been a military fortress, a palace, a royal mint, a prison, a zoo and a place of execution, a silent witness to some of the most momentous events in our history. Dan Jones reveals some of its secrets and tells the stories of the traitors, rebels and royalty who met their end inside its imposing walls.

Today Warwick Castle is a popular tourist attraction, but for centuries its walls echoed with the sounds of betrayal, bloodshed, murder and financial ruin. Dan Jones reveals the turbulent history which took place within the well preserved walls of this imposing castle and the tales of the earls of Warwick who lived there.

Situated high on a crag overlooking the river Forth, Stirling Castle has guarded the gateway to the Scottish Highlands for centuries. The residence of kings, armies and felons, its battle scarred walls have witnessed savagery and chivalry, intrigue, adultery and murder. Its history includes some of the most charismatic characters in Scottish history.

Dan Jones explores the turbulent history of Carrickfergus, one of the most ancient castles in Northern Ireland and a stronghold that holds the key to understanding the tempestuous relationship between Britain and Ireland from the Middle Ages to today.