Every woman in the land is secretly Mrs Darcy

I came home from work unexpectedly early the other day and surprised my fiancé in the act of secretly watching reruns of Andrew Davies's Pride and Prejudice. It turns out that Elizabeth Bennet is his favourite woman in literature – not as played by Jennifer Ehle necessarily, although I don't suppose that does any harm, but the real one as written by Jane Austen. Naturally it is very flattering to learn that one's fiancé is a long-term admirer of Lizzie Bennet. (I mean, who would want to marry someone whose literary heroine is, say, Anna Karenina?) But my, those are big shoes to fill. For an actress, of course, as well as for a wife.

Strangely, though, the announcement of the cast for the new BBC adaptation of P D James's Death Comes to Pemberley has led to a lot of sympathy for the actor who plays Mr Darcy. The book is a crime story set in the Darcy-Bennet household six years after their wedding, when they already have two children. Matthew Rhys will play Mr D, and everybody wants to know if he thinks he can out-Darcy Colin Firth, and whether he plans on emerging from any ponds.

Rhys immediately tried to brush aside the idea that he might feel any pressure from the spectre of a soggy Colin Firth peering over his shoulder. "The beauty of Pemberley is that it is an entirely new and different Darcy, six years on," he said. "Also, I don't have to appear from a lake in a white shirt and breeches." But the one who should really be worried is Anna Maxwell Martin, who plays Elizabeth.

Trust me, there are no bookish boys who grow up reading Pride and Prejudice and thinking that they are just like Mr Darcy. (Plenty of men are like Darcy – "He has no emotional vocabulary," as Rhys generously puts it – but those ones did not spend their formative years reading Jane Austen.) On the other hand, many generations of female book geeks have convinced themselves that Lizzie Bennet is entirely based on them.

Unlike any other classic literary heroine – the tragic beauty Tess Durbeyfield; the kind-of annoying Emma Bovary; the downtrodden Jane Eyre ("Reader, I married the slightly-singed, good-for-nothing attempted bigamist") – Lizzie has female readers wanting to be her from the start. Who doesn't want to say to her suitor: "Now be sincere; did you admire me for my impertinence?" and when he replies "For the liveliness of your mind, I did," retort "You may as well call it impertinence at once. It was very little less"?

Lizzie is not beloved for her beauty, as most young book geeks will also never be. She's not a simpering little wannabe-wife. She's just bloody brilliant. Fortunately, so is Anna Maxwell Martin, who has form in the strong literary heroine role. She's not a Hollywood beauty, though she is striking. She has that determined, Bennet jut of the chin. And she's absolutely nothing like Keira Knightley. She may not have to wade out of any water, but Maxwell Martin has nothing less than many women's ideal self to portray. Good luck to her with pulling that off.

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