First there was Michelle Gomez's return as Missy, then there was John Simm's comeback as the Master, and now we've just had confirmation of another special Doctor Who series 10 appearance.

The latest news is not about a returning character, but concerns a new actor joining the cast who has been kept under wraps until now.

Actress Samantha Spiro confirmed during an appearance on BBC Breakfast that she would be appearing later in the series, although she refused to reveal what exactly her role will entail.

“I’ll be in this series of Doctor Who. I can’t say how, I can’t say who, I can’t say where!” she said on the BBC1 show.

The Olivier Award-winning actress was most recently seen in season six of Game Of Thrones as Melessa Tarly, and is set to appear in the BBC Barbara Windsor biopic Babs. She has also previously appeared with Doctor Who writer Mark Gatiss in Sky comedy Psychobitches.

Unlike other guest stars such as David Suchet and Ralph Little, Spiro's appearance has not been revealed until now – her name was not in showrunner Steven Moffat's episode guide at the start of the series.

Has her name been kept back until now for a reason? Who knows...

Doctor Who continues Saturday at 7.20pm on BBC1