Game of Thrones actress Maisie Williams has revealed that her character in Doctor Who may be “good or bad”.

It was officially announced last month that she would be a guest star in the new season and it has been rumoured that the actress will be playing a Viking in the historical story.

Williams told Alan Carr on Channel 4’s Chatty Man: “There’s been a lot of speculation about whether she’s like a younger Clara or whether she is a new character completely. I’m not going to tell you which one.”

She added: “Whether she is good or bad is up for discussion, I think. She does put the Doctor to the test and it’s sort of a dynamic that we haven’t seen before.”

On how Doctor Who differs from filming Game of Thrones, Williams commented: “I’m used to being part of Game of Thrones and going into something where you’re a small part of something else. You don’t want to hold anything up because they’ve got such a well-oiled machine going. Everyone is so accommodating and lovely and happy to have me. There’s no rivalry that I thought there would be – ‘You’re from Game of Thrones‘ and I’m like, ‘You’re from Doctor Who‘. They’re really lovely.”

The actress has played Arya Stark since 2011 in Game of Thrones, which returns for a fifth season tomorrow night. She also recently appeared in Channel 4’s one-off drama Cyberbully.

> Take a look at our list of Game of Thrones actors who’ve appeared in Doctor Who.

Doctor Who showrunner Steven Moffat teased last month: “It’s not possible to say too much about who or what she’s playing, but she is going to challenge the Doctor in very unexpected ways. This time he might just be out of his depth…”

Season 9 began filming in Cardiff in January and will air on BBC One this autumn.

> Here’s everything we know about Season 9 so far.

Are you looking forward to seeing Maisie Williams in Doctor Who? Who do you think she’ll be playing? Let us know below…