Dame Jacqueline Wilson is to release her first adult novel since the 1970s as she returns to her beloved Girls series.

The 78-year-old bestselling author, who lives near Alfriston, will revisit the lives of Ellie, Magda and Nadine who are now faced with navigating the highs and lows of adulthood.

The new novel, titled Think Again, will be released in hardback, audio and ebook this September.

The original four-part Girls series began with 1997’s Girls In Love, followed by 1998’s Girls Under Pressure.

Girls Out Late was released in 1999 and the series concluded with Girls in Tears in 2002.

Narrated by teenager Ellie Allard, the books followed her and her best friends Magda and Nadine as they experienced life and love.

The first novel was also adapted into a TV series with the same name which aired from 2003 to 2005 on CITV.

The new novel will pick up with Ellie now as an adult who has a daughter Lottie and a cat named Stella, as well as her best friends Magda and Nadine still by her side.

However, her love life is described as “non-existent” and she is “living on auto-pilot, just grateful to be able to afford the rent on her pokey little flat”, the publisher said.

“But this year, on her 40th birthday, the universe seems to decide it’s time for all that to change – whether Ellie wants it to or not”, the synopsis adds.

“As she navigates new, exciting and often choppy waters, she’s about to discover that life will never stop surprising you – if only you let it.”

Dame Jacqueline said: “I’ve always wondered whatever happened to Ellie, Magda and Nadine, the teenagers in my Girls series. I’ve decided to find out what they’re up to nowadays.

“It’s been great fun writing for adults for a change. I think everyone reading Think Again will be surprised.”

The author, a former Children’s Laureate, is also widely known as the creator of Tracy Beaker as well as her other children’s novels including Candyfloss and Double Act.

Her agent Caroline Walsh said: “Over the years, I’ve seen endless heartfelt pleas from Jacqueline’s readers for an update on the girls’ lives so it’s hugely exciting to see that dream become a reality at last.

“As Jacqueline knows only too well, life can take you on the most amazing journey and in Think Again, Ellie both fulfils past dreams and finds new ambitions to guide her into the future.”

Dame Jacqueline’s adult fiction editor Thorne Ryan said it was a “complete dream” to work with the author having being a fan throughout her life.

Ms Ryan added: “I’ve reread the Girls series many times over the years, so it is such a joy to rejoin Ellie, Magda and Nadine as they navigate the highs and lows of adulthood.

“Through them, Jacqueline explores themes such as expectation versus reality, self-discovery, and the need to push yourself beyond your comfort zone to achieve fulfilment.”