How does a character that’s spanned years of a writer’s glittering career get given a send off? If you’re acclaimed author Lynda La Plante, then that famous character doesn’t go quietly or without a fight.

This month, our most famous female detective, Jane Tennison, is being sent on her Prime Suspect way, with La Plante’s final Tennison crime instalment, Whole Life Sentence, out from July 4.

The final book ends where Prime Suspect begins, with young Jane leading the murder squad and their hunt for a serial killer.

Getting to know ‘young Jane’ has been a 10-year endeavour for 81-year-old La Plante, given it’s a character she’s taken from her early 20s through to her late 30s.

“Every book on Jane Tennison, the young Jane Tennison, has taken her through every single problem to the age that Jane Tennison was in Prime Suspect,” explains the former actress from Liverpool, now a globally famous author, as we speak over Zoom.

“So each book stood up by itself as a story as she went up in rank, and up in rank, and up in rank. And you know, the reason I even wrote the young Jane Tennison was because at an event, a woman said to me, ‘What was Jane Tennison like as a young girl?’ And I had no idea”.

In 1991, police drama Prime Suspect made its debut with Dame Helen Mirren as hard-edged Detective Chief Inspector Jane Tennison.

Prime Suspect, inspired by the experiences of ex-Flying Squad officer Jackie Malton, was a sensation for ITV, catapulting Dame Helen to international fame. Across its seven series the show won six Baftas, the Edgar Allan Poe Writers’ Award and an Emmy for best mini-series.

In 2015, La Plante brought back the detective in the first of a series of prequel novels as young Tennison, rewinding to the Seventies as the eponymous 22-year-old newbie is drawn into her first murder case.

“I’d never gone back into what was she like. So it was very interesting to work on,” says La Plante.

“One time, when there were no mobiles – I love one of the books where somebody does get one of those big mobile phones in – and she says ‘I don’t think they’ll catch on’.

“And it was nice to go through her personal life, her romances, her failures, and also, by the time this book comes out, she’s reached the level she’s been fighting for, for her entire career.”

Career milestones are something La Plante has plenty of. In January this year she was named as a recipient of the Diamond Dagger, the highest accolade from the Crime Writers’ Association (CWA), where she was honoured for her outstanding contribution to crime writing.

And come September her memoir Getting Away With Murder will be published.

Starting as a graduate of the Royal Academy of Dramatic Art (Rada), as an actress in her early days she appeared in a number of classic TV series including The Professionals, The Sweeney and Minder.

Her debut novel The Legacy was published in 1987 following her writing the 1980s crime series Widows about armed robbers’ wives.

“I’m able to introduce all the characters from the original Prime Suspect. There she is, ready, I’ve made it. And she is met with more discrimination,” she says.

“The misogynistic attitude towards her is unbelievable. It’s unremitting, it never stops. And she gets to a point to say, ‘I’m going to throw the towel in, I can’t do it’. But something in her says, I will fight you on every single level. And so in the last book, we see the fight commence…”.

“What you see in the last book is it’s not actually the end, it’s the beginning, but you see, my God, that woman fought every inch of the way. So it just swings into Prime Suspect and it’s been wonderful to bring back those characters. I’ve loved it”.

The farewell to Tennison is one the author ready to say though.

“Because in the end, she’d live with me for an awfully long time and the relief of moving on to other characters like Jack Warr (another detective she created), is good because it means that I have to keep on stretching myself over and over again to make something as good.”

Prime Suspect broke barriers on its release, as Tennison battled sexism and prejudice in a male-dominated profession, refusing to be undermined by colleagues who questioned her seniority and ability.

Asked if she had always intended for Tennison’s fighting spirit to be the voice for women not being recognised in the police force, she recounts an anecdote about retired detective Malton, who helped her craft the Prime Suspect characters.

“I was at a literary function and Jackie Malton, who was my guiding light through the first writing of Prime Suspect… she’s amazing.

“But she came up to me and she very quietly, she gave me a hug, and she said, ‘You changed my life. Thank you’. And it meant so much to me, because I was not the champion saying, I want to make any great forward movement for the women, I had constant mirror images coming at me. You know, they were there,” she says.

“People were coming up to me all the time. So because of their wonderful attitude to me, in research, for me, I just wrote it down.

“Sometimes I’ve flicked in a bit of stuff that might be from my own… You know, she’s the most inept person at choosing the good man.

“And what’s so wonderful is, I know people are reading it saying, ‘This is not going to work. No, you’ve got the wrong one this time’.

“I’ve thrown a few of those times of my life in there, but the most important thing for me was to get her real, to be truthful”.

She reflects on the realities of being a police officer, having done her fair share of research over the years.

“I don’t think you can ever really know what it’s like, how much emotion they have to go through as a police officer, male and female,” La Plante muses.

“You can get all the training in the world, but there’s no training for you to be able to control that moment where you knock on a door…. no training to say to a couple, ‘We have found your daughter’.

“And over and over again, what used to come back to me were the crimes that they had buried but never forgotten. Writing crime is one thing, you can end it and it’s finished. But in real life, it’s never finished. It’s never over”.