' You wouldn't believe some of the things I've seen," says queen of crime fiction Lynda La Plante before launching into an uproarious and horrific tale of a research trip to a Russian mortuary.

I'll spare you the details but it involved dodging rows of hog-tied bodies her Russian guide took great glee in swinging.

"This little, round Russian woman set them swinging like dominoes and then stood back, clapped her hands and cackled, 'Bang, bang!'. My interpreter fainted in front of me! It was horrific! Worse than that," says La Plante, laughing, "the film never got made!"

La Plante's latest novel Good Friday - the third prequel involving her most celebrated protagonist, Prime Suspect's Jane Tennison - didn't require such gruesome research as London in the 1970s was a city she knew well.

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"Oh, but I had such a great time in my 20s and 30s in London, I really did," she says down-the-line from the Hamptons, where she lives part of the year. She also keeps a house in London and says just as she starts to get bored with America, she goes home and gets bored in England.

The famous Balcombe St siege - watched live on TV by millions in 1975 - occurred just around the corner from where she lived and despite the IRA's activities, La Plante, now 74, considers it a much more innocent time. Even terrorists then, played by the rules.

"Before a bomb was detonated, the IRA would ring Scotland Yard and give a code that was recognised; they'd tell them that a bomb is here and will go off at this time," says La Plante. "So the police had time to defuse it; when they didn't have time it would blow up. Now terrorism is so much more terrifying and random; driving a van into innocent tourists and people walking across London Bridge, that's just crazy."

In the 70s, La Plante was an aspiring RADA-trained actress, working repertory all over London. The flat Tennison lives in in Good Friday is the same one La Plante occupied at that time. She studied with Ian Mc Shane and the late John Hurt, among others, working both on screen and stage.

But her big break happened off-camera when she created and wrote Widows - about four women who team up to complete an armed robbery after their husbands are killed on the job - for Thames Television in 1983.

That show is getting a second-life as a Hollywood blockbuster, starring Liam Neeson, Colin Farrell and Viola Davis with Steve McQueen directing. While La Plante had no input into the script, which is being handled by McQueen and 21st century crime fiction star Gillian Gone Girl Flynn, La Plante took the opportunity to update Widows before the film's release next year.

Though Widows got La Plante noticed, it was 1991's Prime Suspect which would make her a global force. She cast Helen Mirren in Prime Suspect - in what turned out to be a star-making role - saying as soon as she saw Mirren, she knew she was perfect for the part.

"The breakthrough of Prime Suspect was showing an incredibly determined, dedicated police woman, who was the right age; often on TV shows you see 20-year-olds with a very high rank. It just doesn't work that way."

Good Friday Lynda La Plante (Zaffre, $37)
Good Friday Lynda La Plante (Zaffre, $37)

La Plante now intends to write six more Tennison prequels to bridge the gap until we arrive at the character viewers know. "When we meet Jane in Prime Suspect she's in her 40s. It was fascinating to go back to when she was only 22 and see how that character formed and how she became that cool, tough woman Helen Mirren plays. After Good Friday, Tennison's going to be moving up a notch every book - both in her personal life and in her career."

The three-part series Prime Suspect 1973 aired earlier this year in Britain to middling reviews; La Plante was attached to it but walked away when major creative differences surfaced.

"The entire episode was the worst time of my life," she says with an audible shudder. "The series that came out of ITV was not mine. I just walked away, I couldn't take it. They wouldn't have one actor that I wanted, the director refused to read my book, which the show was based on, and it was handled by a production company that had never produced anything before! It was a nightmare, the worst experience in my professional life."

It means any future projects will most likely be controlled in-house at her production company - and she still hopes to turn her forthcoming Tennison books into a TV series. She still gets up at 4.30am to write ("four hours every day"), runs a production company and catches up on her crime shows - Bosch, Big Little Lies and Goliath are current favourites.

The almost complete lack of DNA technology and mobile phones also attracted La Plante to setting stories in the 1970s. Detectives back then, she says, really earned their keep, which in turn keeps a writer on their toes.

"There was very minimal research into DNA at that time. And no one had mobile phones, yes, there were a few police phones but they often didn't work. And back then they didn't wear white paper suits when dealing with a body - not at all - they'd trample all over it - often smoking cigarettes! There was no sense of what DNA and detail could be gathered from the location and position of a body."

During a five decade career, La Plante has become something of a forensics expert herself and was made a Forensic Science Society Fellow in 2013 in honour of her accurate portrayals of forensic science in her shows and books.

"Because I have spent so much time working with forensic teams and in laboratories, their fingers are over everything I write," she says. "I really do spend a lot of time researching and I want to get it right, that's important to me. Once I had a plot point that involved Luminol and my expert told me - 'Sorry, Lynda, the British police don't use it.' Well, six months later they did, so back in it went."

Her familiarity with the dark side of human nature hasn't inured her to the impacts of crime. She refuses to write about child murder because she has seen the impact it has on officers and the people involved.

But La Plante saves the best news to last when she tells me she plans a series set in New Zealand and Australia. "It's very exciting. It's early stages but I'm working with a wonderful lady I met who is a high-powered New Zealand profiler I can't name just yet. She's going to help me get the facts right. I'm hoping to write a series set on a famous New Zealand case, which will be both a TV series - which we film in New Zealand - and a novel."

Lowdown:
Good Friday by Lynda La Plante (Zaffre, $37)