Born to a Scottish mother and Chinese father, Siu lived in Hong Kong until the age of 4, before moving to Scotland. Beginning her career in theatre and appearing in short films, her first major television role was as Echo in the CBBC series "Dixi". She became known to larger audiences following an appearance in 2017 zombie musical "Anna and the Apocalypse" as Lisa and also for the role of Kyra in teen spy series "Alex Rider".
It's the wit and humour that she will bring to the role of Nell that we're looking forward to, as she revealed to the BBC. "In the script, Nell came across as very witty, articulate and funny, with a lot of one-liners. In a lot of scripts, they are usually reserved for the male characters but in this, I think she has some of the best!" Siu explains.