We realised we could think of several well-known male writing friendships: Coleridge and Wordsworth for instance, or Byron and Shelley, Fitzgerald and Hemingway. But when it came to the most celebrated female authors, we found ourselves at more of a loss.

For approaching two decades now, my close friend, author of Owl Song at Dawn Emma Claire Sweeney, has been my bedrock of writerly support.

For years, we have critiqued stories-in-progress, passed on news of publishing opportunities, lent a sympathetic ear during those times when it felt like neither of us was going anywhere fast.

Talking together one day about how much we’d come to rely on each other’s help, we began to wonder whom the famous authors of the past turned to during their own times of need.

We realised we could think of several well-known male writing friendships: Coleridge and Wordsworth for instance, or Byron and Shelley, Fitzgerald and Hemingway. But when it came to the most celebrated female authors, we found ourselves at more of a loss.

Did Jane Austen have a confidante she called on for literary advice? What about George Eliot? Or Virginia Woolf? We’d heard that Charlotte Bronte had been a friend of the Cranford author, Elizabeth Gaskell. But they had become acquainted near to the end of Bronte’s life. Was there anyone else, other than her author sisters Anne and Emily, to whom Bronte could turn for support?

Out of these questions and the research it inspired A Secret Sisterhood was born – a non-fiction book on female literary friendship, which I have co-written with Emma.

Following hours spent deep in the archives of museums and libraries on either side of the Atlantic, we pieced together the stories of the literary bonds between four of the western world’s most respected female authors.

We found that Austen – often regarded as a genteel lady scribbler, devoted above all else to hearth and home – in fact risked the disapproval of her family to maintain a friendship with keen amateur playwright Anne Sharp, a member of the Austens’ household staff.

In addition to the influence of her famous sisters, Bronte’s work was also shaped by her friendship with the feminist author Mary Taylor, who she met at boarding school. Taylor encouraged the literary ambitions of the future author of Jane Eyre, and convinced Bronte that she should accompany Taylor for a period living in the Belgian capital of Brussels – where she would scandalously end up falling in love with a married man.

Rather than being the rather aloof individual of popular imagination, Eliot enjoyed an intimate transatlantic bond with fellow literary legend, Harriet Beecher Stowe, famous for Uncle Tom’s Cabin. Although they could never meet, they nurtured their bond through a series of deeply personal letters that came to an end only with Eliot’s death.

Often dismissed as merely bitter foes, Virginia Woolf and fellow Modernist author Katherine Mansfield had a tempestuous yet genuinely close friendship, lit by an underlying erotic charge. After Mansfield criticised Woolf’s second novel Night and Day for failing to dwell enough on the changes wrought by the First World War, Woolf went on to explore this subject in her three subsequent novels.

In writing our own book, on literary friendship between women, Emma and I have come across many examples of female writers going out of their way to support each other – both in the historical documents we’ve studied and in our experience of having other writers devote their own valuable time to help us.

The most unexpected of these encounters occurred very late in the writing process, when the Booker Prize-winning author of The Handmaid’s Tale Margaret Atwood – someone whose work we had long admired but who we didn’t personally know – agreed to write the foreword for our book.

Atwood’s generosity in taking the time and creative energy to champion our project has firmed up the sense we’d gleaned from our years of research. Not only has there always been a ‘secret sisterhood’ of writer women doing their best to support each other, today, in 2017, it is still very much alive and well.

A Secret Sisterhood: The Hidden Friendships of Austen, Bronte, Eliot and Woolf by Emily Midorikawa and Emma Claire Sweeney (Aurum Press) is out today.

They will be in conversation with author and playwright Samantha Ellis at Waterstones Crouch End on Wednesday June 7, 19:30. £4, 020 3551 9706.