Born: 15th April 1997 (as Margaret Constance Williams)
Episodes Broadcast: 2015

Margaret Williams was born in Bristol, and was given the nickname “Maisie” as a child because she was thought to resemble the little girl of the same name in the long-running Daily Mirror comic strip The Perishers. As a child, she aspired to be a professional dancer and attended the Susan Hill School of Dancing in Bath, Somerset. This prompted Williams' involvement in talent shows, which led to her acquisition of an agent who encouraged her to try her hand at acting. At the age of twelve, she was cast as Arya Stark in the groundbreaking fantasy series Game Of Thrones, which debuted in 2011. Between seasons, Williams appeared in programmes such as The Secret Of Crickley Hall. Her first movie was the 2013 thriller Heatstroke, which she quickly followed with the comedy Gold and the mystery The Falling. Williams also starred in, and executive produced, a 2013 short film called Up On The Roof. Although she began to study performing arts at the Bath Dance College, she decided to leave school at fourteen years old to concentrate on her acting career.

Williams' appearance in the telefilm Cyberbully, broadcast at the start of 2015, persuaded the Doctor Who production team to offer her the recurring role of Ashildr in the run of episodes that would air later the same year. She made her debut as a Viking girl in The Girl Who Died, before returning for three more episodes by virtue of the immortality which the Doctor had unwittingly thrust upon her. Williams' last appearance came in the season finale, Hell Bent. She subsequently made movies like iBoy and Mary Shelley while becoming involved in voice acting; having previously contributed to Robot Chicken, she could now be heard on the silver screen in Early Man and on television in gen:LOCK. In 2016, Williams co-founded Daisy Chain Productions with a view to developing more British short films. She also collaborated on an arts-focussed social media app called Daisie, which launched in 2018.

During the Twenties, Williams starred with Seventh Doctor Sylvester McCoy in the thriller The Owners, as well as the long-delayed Marvel Comics super-hero movie The New Mutants. She returned to television for Pistol. In 2021, Williams became the World Wildlife Fund's first global ambassador for climate and nature.