"She's obviously very tough, but is also very funny," says Sharon of her character Lynne Warner.
"Her son was killed in Afghanistan, and that's how she has 'bought' the presidency for the President – not financially, but emotionally. Because of the death that she endured and the way she handled it. It brought America to her side. That has made her the most powerful American in the show, because the President listens to her and does what she recommends.
"She and Mark Brydon respect each other very much. They're very complex characters who start off as allies, but become enemies for a while because of a lot of false information."
Sharon, best known for playing one half of American cop duo Cagney and Lacey, thinks Lynne is more sophisticated than her earlier alter-ego.
"Cagney was more petulant, more immature. Cagney was an angry cop with a mouth on her, who had dreams of becoming the first female police commissioner and was driven almost in an unhealthy way.
"Lynne is much more controlled, much cooler. She may be a hothead inside the room, but never to her detriment. Cagney had no respect for authority at all, but Lynne does respect her President."
"Lizzie Mickery and Dan Percial have written me wonderful stuff. I had to give the script three reads because it's very, very complicated. I just knew I had to be part of it. It's the kind of character I've simply never played before."
"And I'm working for the BBC – that's such a thrill! I've done radio for the BBC before, but never film. Then I heard about all these wonderful actors they were bringing over from London, and I thought, 'I'd like to be in that'. So I met with the producers and here I am!"
