Every so often the BBC announces that it has shown enough costume dramas and will henceforth be concentrating on contemporary stories. But still the costume dramas come, proof of their popularity with audiences at home and abroad, where they do no harm to the BBC’s bank balance. So it is that J.K. Rowling’s unsettling The Casual Vacancy has been followed by Poldark (8 March), a much more traditional piece of Sunday-night viewing. The first version of this saga, shown between 1975 and 1977, ran to 29 episodes and was sold to 40 countries. The new one, eight episodes in total, is as glorious and preposterous as its predecessor. Ross Poldark (Aidan Turner) is a perfect romantic hero; he has the looks – dark, brooding, with unruly black hair and a scar – and he has the