Half a millennium before the Romans first arrived in Britain, an even more ferocious people, the Celts, arrived in what is now south-eastern England. The Celts remained in Britain long after the Romans departed, and although driven into the remoter corners of the island by English invaders the people who remained clung onto their Celtic heritage, and defended their remaining lands against all-comers. In order to defend their lands from other tribes or outside invaders these people established powerful fortified sites that served as places of refuge in wartime and as administrative and trading centres in times of peace. This book examines these fascinating forts, which varied considerably from the mysterious brochs and duns found in northern Britain, to the hill-top forts ranging in size, to the promontory forts that formed powerful coastal strongholds all around the island's shores.