The skies are stormy and the rain lashing down when Elly Griffiths opens the door at her Saltdean home. Replace the chalky South Downs with the flat plains of Norfolk and it could be a scene from one of the author’s bestselling Ruth Galloway crime novels.

But the sense of foreboding swiftly dissipates as Griffiths bustles around the kitchen making coffee and trying to locate the family cat Gus, who will appear in the photographs with her. It’s important, she says, to underline her feline-friendly credentials; one of her plotlines involved a cat being killed and she continues to get angry letters about it.

Griffiths’s fans are a devoted bunch, you see, constantly badgering her for clues about the next book or begging her for more sex scenes – “Little old ladies!” she laughs. “Unbelievable!”

In the years since she wrote The Crossing Places, the first Ruth Galloway book, back in 2009, readers have become fiercely loyal to the overweight and underpaid protagonist, a forensic archaeologist with a dry sense of humour and a weakness for a certain Harry Nelson of the Norfolk Police Constabulary. At a recent crime writers’ convention in the US, one woman even told the author she began every day by asking herself, ‘What would Ruth Galloway do?’ Griffiths is amused and delighted. When she wrote the first book she had no idea it would become a series; she didn’t even realise it was crime. It was her publisher who categorised it and advised the half-Italian writer to drop her real name – Domenica de Rosa – in favour of something grittier.

She chose the name of her Welsh grandmother, whose dreams of being published were never fulfilled.

Griffiths (we decide to stick with Griffiths for the sake of clarity) had already written four novels under her real name after rediscovering her love of writing while on maternity leave from her job with Harper- Collins. Then Ruth Galloway appeared to her on a walk across the Norfolk marshes.

“I hate saying this – I teach creative writing and it’s something that hardly ever happens – but Ruth really did arrive fully-formed. I knew her name, I knew the sort of biscuits she liked.”

Griffiths’ husband Andy had recently retrained as an archaeologist after a career in the City and the family’s exotic holidays had been curtailed in favour of cheap breaks to Norfolk, where Griffiths had spent summers as a child.

As he explained prehistoric beliefs about marshland – as a liminal space that is neither land nor sea, it was believed to be a bridge to the afterlife – she was struck by an idea that would become The Crossing Places, which sees Ruth Galloway brought in to examine bones thought to be those of a little girl who went missing a decade earlier.

The book, which also introduced favourite Griffiths themes of witchcraft, ritual and folklore, went on to win the 2011 Mary Higgins Clark Award, which honours the best suspense novels written by women.

A lot has happened since then; the Ruth we meet in the fifth novel, Dying Fall, is a single mother to baby Kate, and Cathbad, the ponytailed Druid from book one, has become the child’s godfather.

In addition to investigating the unexplained death of her old university friend, a brilliant academic killed in a suspicious house fire, Ruth must contend with the more prosaic trials of being a new mother.

There aren’t many protagonists in crime fiction with soggy rusks in their pockets but then Ruth Galloway isn’t exactly the standard female lead.

Griffiths didn’t set out to write her as some sort of antidote but she was struck, she says, by the abundance of “superwomen”

in the genre.

“All the female characters in crime seem to run before breakfast and cook gourmet meals while going through an old case…it didn’t seem very realistic. Ruth is a bit overweight but happy in herself.

She’s not fatally flawed, just rather unglamorous. I think she’s quite typical of an academic type.”

The series has recently been optioned by the BBC and while Griffiths is trying to keep out of it – “You don’t want to end up writing books for the actors playing your characters” – she admits it is “impossible” not to entertain a few thoughts about who might end up playing Ruth.

Her first choice would be Gavin & Stacey actress Ruth Jones who looks “exactly how I’d imagined Ruth”, while she rather fancies Richard Armitage (Thorin from The Hobbit and Lucas North in Spooks) as the rugged, deadpan Harry Nelson.

The series could lend an unlikely glamour to Norfolk, a brooding, eerie place that’s as integral to the Ruth Galloway novels as Brighton is to Peter James’s Roy Grace series.

Griffiths spent many summers there with an impressivesounding aunt who had a boat on the Norfolk Broads and filled her niece’s head with stories about ghosts and water spirits, and she continues to be fascinated by its desolate landscape.

But Sussex has also played its part. Brighton’s Booth Museum is transposed to Norfolk in A Room Full Of Bones, in which the curator of King’s Lynn Museum is found dead beside a coffin “All the female characters in crime seem to run before breakfast and cook gourmet meals while going through an old case… it didn’t seem very realistic Saltdean author Elly Griffiths talks to Nione Meakin about creating a realistic protagonist in the shape of overweight forensic archaeologist Ruth Galloway containing the bones of a medieval bishop, and the writer regularly draws on the expertise of local archaeologist Dr Matthew Pope, and Lucy Silbun, a real-life forensic archaeologist who works in West Sussex.

“I don’t tend to go on digs, they’re too much like hard work and you can’t have a cappuccino, but I love all the stories. I’ll often call on Lucy or Matthew if I’m trying to work out a twist – why something might not be what it appears to be.”

When we meet, The Outcast Dead, the sixth Ruth Galloway novel, is on its way to the printers for release early next year and pages of the seventh book are open on her computer in a cosy study. She plots each chapter with a single sentence before beginning to write. “I always know who did it before I set off. It amazes me that some authors change the culprit halfway through.”

Yet even she is unsure how one plotline will end. “I genuinely don’t know what’s going to happen with Ruth and Nelson and their on/off relationship,”

she says with a smile. “It’s the thing I’m asked about most.

Lovely old ladies come up to me and tell me I have to kill Michelle [his wife]. One told me if I wasn’t prepared to kill her off then could I at least let Ruth and Nelson go to bed together again? But I really haven’t decided how it should end.

I’ll have to keep on going until I do!”

*Dying Fall (Quercus paperback, £7.99).

*The Outcast Dead comes out in February next year.