Portchester Castle, Hampshire

Portchester Castle is one of the best-preserved Roman buildings in Britain, and certainly one of the most impressive. Like Richborough Castle (featured in the first programme, 'Fact and Fable') Portchester was one of the so-called Saxon Shore forts, and it was built in the third century to protect the province from barbarian pirates sailing up and down the English Channel. The walls are ten feet thick, and over twenty feet in height, and there were originally twenty bastions, of which fourteen have survived.

Signposted off the A27 between Fareham and Portsmouth.