‘When Claire Danes and Tom Hiddleston were cast I was in shock’: Sarah Perry on The Essex Serpent

In March 2021, I was driven by a stranger down to the Essex coast, and there I found myself at the end of the 19th century, in a place that had never existed, full of people who’d never been born.

At any rate, that was the impression; in fact, I’d been deposited in a field on Mersea Island, which is cut off from the Essex mainland by a causeway inaccessible at high tide. Filming was under way for an adaptation of my novel The Essex Serpent, and since Mersea was one of the locations making do for Aldwinter, the imagined village where the novel is set, I’d been invited to take a look. The field had been colonised by a series of trucks and trailers, and everywhere I looked crew members were dashing about with clipboards and headsets, occasionally interspersed with actors in top hats, or in petticoats inches deep in Essex mud.

I know Mersea well, and had last visited with my goddaughter, so as I walked about there was the strangest sensation of double familiarity. On the one hand, there were the same old wooden cottages, and the same sea wall with shingle below it, and the cafe where we often bought ice-cream – but overlaying it all was Aldwinter, familiar to me only because I’d invented it. Down on the quay, a fire hose was doing the work of high tide, and seaweed had been scattered about; concrete bollards had been concealed by wooden crates, and fishing nets were hung over garden walls to dry. Everywhere there was an atmosphere of diligent hard work, as crew members adjusted baskets for eels, or children wandered past in shawls and clogs, but there was also the eerie atmosphere peculiar to that part of the Essex coast. It was Aldwinter to the letter, and astoundingly uncanny: it was as if the acts of writing and reading had been bypassed entirely, and the whole thing had leapt clean out of my skull.

As I arrived, filming had begun on a scene in which Aldwinter’s vicar Will Ransome (played – perfectly, in my disinterested opinion – by Tom Hiddleston) is briefly seen remonstrating with his sanctimonious verger outside the village school. The director Clio Barnard and the screenwriter Anna Symon welcomed me with characteristic kindness and I was given a headset, and shown the action on an iPad. Over and over, without once appearing to grow weary or impatient, the actors worked diligently at the brief scene until it was right, and the sight of this moved me almost to tears. That the story I’d written in a small, cold room in a Norwich terrace would one day be accorded such extraordinary care by so many people was remarkable, and I went to sit on the quay with a solitary cigarette, looking at the Thames barges moored nearby, trying to accommodate it all.

I suppose it would be usual for a writer to daydream about this sort of thing, but I never did: I’d allowed myself only the hope of kind reviews, and the means to pay the council tax on time. So the year of publication had constituted a series of wonderful shocks, one of which was finding myself in the offices of See-Saw Films, the production company that optioned the novel. Largely I remember an immense bearded lurcher taking up a sofa in the corner, and a sensation – quite rare to me – of deep shyness. I was treated by the prospective producers with great care. Was there anything in particular I felt should be done with the novel? There was, I said, screwing my courage to the sticking place: keep it gothic, and keep the women real. To the lasting confusion of a number of readers, the novel depicted women as they were in the 1890s – not fainting away in violet-scented swoons and never allowed beyond the withdrawing room without a chaperone, but vital, intelligent, lively and well-educated people, involved in politics, social justice and the sciences, and I felt if that was lost, the betrayal would be far worse than an injustice against fiction. They gave me their word, and I left the meeting assured the book was in the right hands, and promptly forgot all about it.

I forgot partly as an act of will. I’d been cautioned to expect agonising delays: there was casting to be seen to, of course, and all sorts of machinations regarding funding and distribution. Now and then I’d be given good news, and occasionally bad; but already I was coming to the end of my third novel, and was conscious of the dangers of dwelling on a moment of professional success, and never moving beyond it. I’d done my work, and handed it over: I didn’t feel it was any of my business. Besides, I’d seen Clio’s vision, and read Anna’s scripts, and it seemed to me then – and it certainly seems to me now – that in fact they’d amplify the novel as they altered it, so that the TV series and the book would be happy companions, neither cancelling the other out. Still: it was extremely difficult to maintain such a stern grip on myself when Claire Danes and Tom Hiddleston were cast, and I’m afraid on one occasion I forgot myself so far as to lie face down on the carpet in a state of elated shock.

Often I’m asked if the lead actors resemble the characters as I’d imagined them. The truth is that I give less thought to the looks of my characters than to their interior lives: as I write, I’m not looking at them, I am inhabiting them. Claire Danes, who takes the lead role of Cora Seaborne and is a slight woman of extraordinary poise, doesn’t exactly resemble Cora, who is described as tall and broad-hipped and untidy. It doesn’t matter: the moment she came striding through Aldwinter on a sunny March morning, I saw only my Cora – a woman of warmth and vitality and intellect, hardly able to contain her lust for the world, and nothing like as wise as she thinks she is.

Related: From Loch Ness to the Essex Serpent, why are humans so keen to invent sea monsters?

Now and then, the experience has proved melancholy. The novel was published six years ago, and sometimes I’ve melodramatically said that the woman who wrote it is dead. I was 35 when I wrote the final pages: much is changed and lost since then. The series, like the novel, is optimistic and even radical in its treatment of intimacy, affection and wonder, and I suspect I’ve grown a little harder and more cynical in the years that followed. Returning to the novel – on one occasion in corsets and teal-blue Victorian gown as an extra at the Natural History Museum – has been like passing my past self on the stairs, always with a pang of affection and loss.

But earlier this spring, as I was shown the series in a tiny Soho cinema, there was only pleasure and delight. All I could do was thank the director, and the writer, and everyone within earshot – because it isn’t pride I feel, it’s gratitude. There had been a time during the pandemic when I’d come to feel that the pursuit of literature was more or less worthless, and that I ought to have devoted myself to medicine, perhaps, or the law. To witness the years of diligence and skill the production entailed returned the courage I’d lost: suddenly the act of storytelling was restored to something noble, and worth the full attention of my life. “What will survive of us,” said Philip Larkin, albeit grudgingly, “is love.” Well: The Essex Serpent is a book about love, that was written with love, and now has been treated with love. I might allow myself to hope it’s what survives of me.

• Sarah Perry will discuss The Essex Serpent and answer your questions at a Guardian Live online event on Wednesday 8 June. Book tickets here. The programme is available on Apple TV+.