Dan Jones explores the history of Carrickfergus Castle in Co Antrim, one of the most ancient castles in Northern Ireland and a stronghold key to understanding the tempestuous relationship between Britain and Ireland. Dan travels to Rathlin island, where he reveals how hundreds of women and children were massacred in the name of Elizabeth I, and visits the tomb of former governor Arthur Chichester, who began a new colonization strategy using scorched earth tactics and laid waste to much of the land surrounding the town.

• Dan Jones