The Booker rules say the prize must not be divided, but the judges insisted they ‘couldn't separate’ the two works. Atwood, 79, is the oldest ever Booker winner, while Evaristo is the first black woman to win.

After their names were called, the pair stood arm-in-arm on stage and Atwood joked: “I would have thought I would have been too elderly, and I kind of don't need the attention, so I'm very glad that you're getting some. It would have been quite embarrassing for me… if I had been alone here, so I'm very pleased that you're here too."

The award's rules were changed after the last tie in 1992, and organisers told this year's judges they were not allowed to pick two winners. But after five hours of deliberations, Peter Florence, the chair of the judges, said: “It was our decision to flout the rules."

It is 19 years since Atwood won the Booker for The Blind Assassin, and 33 years since she was nominated for The Handmaid's Tale. With the latter book enjoying newfound popularity and resonance against the backdrop of Donald Trump's America, The Testaments picks up 15 years after the end of that novel. Returning to the totalitarian, patriarchal Gilead, it is narrated by Aunt Lydia, one of the handmaids' instructors, and two teenage girls.

Peter Florence said: “It does massively more than follow the single story that we had from Offred. This is beautiful in its depth and exploration of the world of Gilead. As [Atwood] has said, it might have looked like science fiction back in the day, although all of the extremities are rooted in fact. Now it looks more politically urgent than ever before."

Published in September, The Testaments sold more than 100,000 copies in the UK in its first week, making it the fastest-selling hardback novel in four years.

Bernardine Evaristo was born the fourth of eight children, in Woolwich, south east London, to an English mother and a Nigerian father. Her father was a welder and local Labour councillor; her mother was a schoolteacher. She spent her teenage years at Greenwich Young People's Theatre, which was where she first became involved in the arts. She went on to study at Goldsmiths, University of London, where she earned her PhD in creative writing. A career in theatre followed and she was a co-founder of the Theatre of Black Women company in 1982.

Girl, Woman, Other is 60-year-old Evaristo's eighth novel. It gives a chapter each to the lives of 12 intertwining characters, who are mostly black British women. “We black British women know that if we don't write ourselves into literature no one else will," the author has said.

Peter Florence said there was ‘something utterly magical’ about the book's characters, whom he said ‘give a wonderful spectrum of black British women today’. “There are stories there of people who haven't been visibly represented in contemporary literature, and in that sense this book is groundbreaking, and I hope encouraging and inspiring to the rest of the publishing industry," he said.

In her acceptance speech, Evaristo said she hoped it would not be long before another black woman won the prize. “It's so incredible to share this with Margaret Atwood, who's such a legend and so generous," she said. “A lot of people say, ‘I never thought it would happen to me', and I will say I am the first black woman to win this prize, and I hope that honour doesn't last too long. I hope other people come forward now."

(Courtesy Agencies)