[8] In 2010, she was a judge for the Biographer's Club Tony Lothian First Biography Prize,[9] the Book Drum Tournament 2010,[10] and the Litro/IGGY International Young Person's Short Story Award.

[12] Williams appears frequently on radio and TV as a presenter and expert, specialising in social, constitutional and royal history.

[16] She appears often on documentaries, discussing history, literature and culture, including Faulks on Fiction and all three series of The Great British Bake Off, as well as documentaries on subjects including Queen Victoria, Balmoral, Sherlock Holmes,[17] Jack the Ripper, Nelson's Trafalgar, Elizabeth II and Hidden Killers of the Victorian Home.

On 13 December 2016 she appeared as a contestant on Celebrity Antiques Road Trip, partnered with Catherine Southon, against Suzannah Lipscomb and David Harper.

[20] In 2020 Williams appeared on Richard Osman's House of Games, broadcast on BBC Two,[21] alongside Chizzy Akudolu, Charlie Higson, and Tom Allen.

[22] In August 2023, Williams appeared in Elizabeth II: Making of a Monarch; a two-part documentary that aired on Channel 4.

[23] Williams was the highest ranked celebrity expert on an episode of the game show The Wheel, which aired on 21 October 2023.