As the saying goes, write about what you know. But what do the rules say when what you know leaves no room for writing?

The mothers of four and three children respectively, both authors are just finding their writing rhythm after decades of balancing parenthood and day-jobs. Read either’s work and the influence of family life is evident, so it is no surprise to hear they will be discussing its importance at this year’s Ham&High Literary Festival alongside Lisa Jewell.

Hornby, as Boyd jokes, has “royal connections”, with her brother Nick and husband Robert Harris already household literary names. The release of her debut novel in May, though, saw the 54-year-old become a bestseller and international success story in her own right.

The Hive, a witty satire of playground mothers and the cliques they form, captured the imagination of a nation waiting outside the school gates and the rights have already been snapped up by a US film company.

Scandalous

Boyd, meanwhile, spent two decades chasing publishers to no avail. Even when Thursdays in the Park was finally published, it only sold 1,000 copies and garnered nine Amazon reviews in its first year.

Upon republication, however, its central story of a grandmother embroiled in an extra-marital affair quickly spread through word of mouth and coined a new genre: “granny lit”. Its reputation continued to swell and Britain was soon falling over itself to read what many were calling 50 Shades of Gray for the over-60s generation. It spent six weeks at No 1 on the Amazon Kindle chart and now has nearly 3,000 reviews.

“That was all a bit silly,” says Boyd of the book’s scandalous image, “but all publicity is good publicity. People bought it thinking it was full of granny sex but there’s barely anything. When my publisher read it actually, she didn’t have many changes, but said she’d like to know if they’d actually ‘done it’. It’s blink and you’ll miss it stuff.”

Having reached her 60s without any encouragement from publishers, Boyd admits she was beginning to lose hope. Now aged 64 and with three novels under her belt, she is paving the way for what Hornby calls the “late developer”.

Hornby’s own back-story is similarly entertaining. After working for years as a regular column writer for The Telegraph, she pitched a story about stranded British tourists in the wake of the Icelandic ash cloud. When they turned it down, she gave it to The Guardian and was promptly let go.

“I got the boot and thought, ‘oh blimey, what am I going to do?’”

The answer, apparently, was to write a novel. “It was a case of ‘if not now, then when?’” she adds. “I’d had the idea since my child was in reception, and with four kids, I already had most of the research I needed.”

When it came to sitting down at the table, Hornby found the biggest obstacle she had to overcome was her self-consciousness. She admits that at first, the concept of naming characters and developing fictitious relationships felt quite “silly”.

“Once I’d written ten thousand words it carried me along though. My whole family as well were very sweet and encouraging. I suppose they gave me a template of how it could be done as well.”

Family will be the focus when Hornby and Boyd come to the literary festival on September 17. As a Highgate resident, Boyd says she’s “thrilled” at the prospect of discussing such an interesting subject with her fellow professionals.

Intrigued

“I’m intrigued by writers in their 20s who can sit behind their desks and detach themselves from everyday life. For me, everything starts with the family, it’s where you’re grounded and how your whole psyche is set.

“The idea of marriage interests me too – one of my old jobs was a marriage guidance counsellor. What keeps people together, what drives them apart?”

Hornby echoes such familial sentiments. With her youngest child aged 12, motherhood is still very much on the mind.

“I could write about family forever, it’s the ultimate drama. Especially if you have four children, there’s always something going on. I know some mothers run million pound businesses whilst raising a family – I don’t know, maybe I can only do one thing at a time.”

n Gill Hornby and Hilary Boyd talk to Lisa Jewell on the complexities of motherhood and family life on September 17. Tickets are £7. For more information, visit www.hamhighlitfest.com