Pevensey Castle in Wealden

You're standing at Pevensey Castle in East Sussex. Really, this is two castles in one. Start with those huge outer walls. They're Roman, built around the year 290, when this fort was called Anderitum. In places they still stand over eight metres high, and at the base they're more than four metres thick. Notice the horizontal bands of tiles running through the stonework? Those are Roman too. No other surviving Roman fort of the period has walls and towers this big.