In a new BBC Four series, historian Sam Willis traces the story of Britain’s castles from William the Conqueror to Queen Victoria. Phil Harper caught up with Sam to find out more.

The second episode of Castles: Britain’s Fortified History is Thursday 11th December, 9pm on BBC Four.

What do you want people to take away from this series?

The series has been conceived and written to encourage the viewer to think about castles in a new way. It raises questions about much of what we take for granted. Often we see a ruined castle and think ‘ah, it has been tumbled-down by time’ but in fact many castles look ruined because someone from the past wanted them to look ruined in the future. The mighty Royal Castle at Kenilworth is a great example. It was deliberately ruined after the Civil War because it was such a powerful symbol of royal authority. When we stand in front of any castle today, our perception of that castle is being manipulated by someone from centuries ago – we are trapped in a web without knowing it, and that bridge between past and present is very intimate.

Are castles still relevant today?

Of course castles are relevant today. They are relics of conflict, permanent reminders of paths we should not tread. I was filming Norham Castle on the Tweed at exactly the same time as the vote was held for Scottish independence. For me, there couldn’t be a better history lesson that in a modern world we need fewer borders, not more.

^{Historian Sam Willis gets ready for filming outside Dover Castle}

Were there any challenges with filming in historic places?

The biggest challenge in filming these beautiful and iconic historical structures is to emphasise their variety. A stone wall, after all, is just a stone wall, but if you visit these castles in person you appreciate just how extraordinarily varied they all are, and the challenge is to get that physical impression of variety across on a small, flat, screen.

In the series you show how many people and events had an effect on the history of the castle. Was there any particular story you found most interesting?

I love the story of Tintagel Castle. I love the fact that this absurd fairy-tale castle was built in a totally ridiculous place that has no strategic or military value whatsoever. If there is one castle that makes you really question the purpose of building castles, then this is it.

Why do you think castles capture the imagination?

They sit in the landscape as massive alien structures that have their own agency – they force you to come up and have a look and ask questions. They somehow need to be explored. We turn up in our nice comfy modern cars, in our warm clothes, fully fed from scampi and chips and a pint at the pub but are stared down by the brutal hulk of the castle. They are historical bullies. They pick you up by the ears, shake you until your knees crack and shout ‘Look at me! Look at what I have been through!’

^{The iconic, picturesque, but impractical Tintagel Castle, featured in the series}

Can you remember where your interest in castles came from? Which was the first one you visited?

I have always been interested in castles and I am not alone in that. I was brought up in Hertfordshire so the first castle I visited was the brilliant Norman motte and bailey at Berkhamsted. Mottes were very good defensive features but they are also excellent for children to run up and down.

Which job would you most like to have done in a medieval castle?

Castles were built to keep people out and to keep people in, which means that I would like a job that would take me both in and out of the castle. I don’t like being constrained. So for me the answer is obvious – I would be part of the hunting parties that rode out and spent all day in the woods trapping and shooting game and bringing it back to the table. I would have a good horse and several dogs to look after and several companions in the same job, so I would be warm, entertained, challenged during the day and then – of course – well fed at night. Who will know if I pocket a rabbit for myself?

Castles: Britain's Fortified History is a three-part series which starts at 9pm on Thursday 4th December on BBC Four.

Want to explore a castle yourself? Choose from over 90 castles here.