In Gentlemen Jack, the actress could not look more different from the brutal, battle-scarred Yara Greyjoy in Game of Thrones.
The BBC drama sees Gemma play Marian Lister and tells the story of her sister Anne Lister’s (played by Suranne Jones) life as an openly gay woman.
She looks totally different in smart nineteenth-century outfits and fans were shocked by the transformation from Yara.
Fans took to Twitter to share their shock at her appearance, with one saying: “Seeing @WhelanGemma in a period dress is just strange. To me she’ll always be Yara Greyjoy, Queen of the Iron Islands. But she is totally amazing.”
Another added: “Yara Greyjoy scrubs up well.”
A third fan compared the two characters she plays, writing: “I didn’t recognise the actress of Yara Greyjoy in Gentleman Jack until she made this face like she wanted to stab someone and I was like ‘oh Yara’.”
Gemma plays a character so different in personality from Yara as well as she plays the uptight sister to Anne.
The drama tells Anne’s story in scenes taken from her diary and charts her scandalous life as a lesbian before the term was even created.
The BBC drama was created by Sally Wainwright and the first episode introduces viewers to business-minded Anne who has moved back to Halifax to sort out her affairs as her uncle chose to leave the estate to her rather than her father.
Speaking to The Mirror, Suranne opened up about the raunchy nature of the period drama and what it was like to film the intimate scenes.
She said: “I was quite nervous about the sex scenes we had to do, because I thought they should be approached as sensitively as they could be.
“One of the great things she brought was an articulacy – we could talk about the scenes.”
The Doctor Foster star worked with sex-co-ordinator Ita O’Brien to ensure the scenes were as authentic as possible.
Discussing Ita’s guidance, she continued: “She just started talking about body parts and positions in a matter of fact way, which just liberated us all.
“As well was helping us sculpt the sex scenes, the positions, she’s also there to provide support to the artists.”
Meanwhile, Yara has not featured much in Game of Thrones season eight and fans have been angry at her absence and what they see as another unfinished plot line in season eight.
One fan said: “If we don’t get Yara Greyjoy tonight, I’ll pull a mad queen on the writers.”
Other fans are speculating she may play an important role jn the series finale, with one tweeting: “Kingdom is split up. Yara Greyjoy rules Iron Islands, Gendry rules southern lands and one of the Starks rules the north.”
Another added: “If there is any justice in this world, Yara Greyjoy will sit on the Iron Throne.”
She was last seen heading off to recapture the Iron Islands in episode one of the season after being reunited with brother Theon (played by Alfie Allen).
Gentleman Jack continues Saturday at 9pm on BBC One.