Haynes was born in Birmingham, where she attended the private King Edward VI High School for Girls.

[7] Haynes was a regular panellist on BBC's The Review Show and was the most-booked guest on More4's The Last Word.

She appeared as a panellist on BBC 4's The Book Quiz, and on its Poetry Special alongside Andrew Motion and George Szirtes.

She also appeared on Backlash, a BBC2 documentary on voluntary childlessness, wrote and performed in the STV/Assembly Television Best of the Fest in August 2005.

[11] In April 2008, Haynes was a member of the stand-up comedians' team on University Challenge: The Professionals.

[13] In February 2022, Haynes was announced as the new presenter of the online revival of Time Team, alongside Gus Casely-Hayford.

Her second non-fiction book, Pandora's Jar: Women in the Greek Myths, was published by Picador in October 2020, and was a New York Times bestseller.

[21] Haynes's third novel, A Thousand Ships (relating to the Trojan War), was published by Pan Macmillan on 4 May 2019.

[24] Haynes's fourth novel, Stone Blind, a retelling of the myth of Medusa, was published by Pan Macmillan on 15 September 2022,[25] and an abridged version was read on BBC Radio 4 by Susannah Fielding.