One of four children born in London, England, to a Greek Cypriot father and a British mother, Leonidas is not the only thespian in the family — her brother Dimitri Leonidas and sister Georgina Leonidas are also actors, whilst her other sister Helena is a teacher.
Leonidas started acting in community theatre when she was eight; at nine she acquired an agent and began to work in television.
Notable credits have included the television drama Daddy’s Girl, the soap opera Night and Day and a 2004 episode of Doc Martin in which she plays Melanie, a local Portwenn 15-year-old girl who develops an unhealthy fascination with the surgeon. More recently she has starred in Neil Gaiman and Dave Mckean’s MirrorMask in the dual roles of Helena and the Dark Princess, and a BBC adaptation of Dracula, as well as Crusade in Jeans. Her theatrical roles have included Adela in a production of Lorca’s The House of Bernarda Alba at Coventry’s Belgrade Theatre, and Dani in The Sugar Syndrome, staged at the Royal Court Theatre Upstairs, London, in 2003. In this latter production, reviewer Lizzie Loveridge said she gave a performance “way beyond her years”.
More recently, Leonidas has once again teamed up with Dave Mckean to work on a new film entitled Luna, which was expected to be released sometime in 2013. She has also recently starred in the BBC made for TV film Atlantis, which aired on BBC one and BBC one HD on 8 May 2011. In 2011 she was in a play for the Transatlantyk Festival called “Influence” and the play was written by Shem Bitterman; Leonidas was Sally, Branden’s girlfriend.