"I can feel myself sometimes sitting in make-up, turning into Margaret. There's a steeliness in Margaret, like an iron rod, and I can feel that taking hold." MacDonald is in New York City, having just wrapped filming for Boardwalk Empire's eight-episode fifth and final season.
The show jumps forward seven years to 1931 and Margaret is still working on Wall Street (where she started working in 1924, at the end of season four). After the stock market crash of 1929, it's a very different place to what we saw last season.
Macdonald is reluctant to give away too much about what is in store for her character in coming episodes but she offers a few hints.
"She's been working on Wall Street for a while and she's working her way up the ranks. Due to some unforseen circumstances that climb is expedited slightly because Nucky gets involved." She reveals "Margaret gets into a little bit of trouble with the law and so Nucky steps in and it opens this other path for her. [Nucky and Margaret] have really not had any kind of relationship for years, not since Margaret's affair with Owen Sleater [Charlie Cox]. She kind of shut that door and moved to New York. It's the next stage of their relationship this season and it is another stage in Margaret's evolution." She says.
When we met Margaret in season one of the show she was an idealistic member of the Women's Temperance League, fighting to support prohibition and rallying for women's rights.
Over the course of the series she has revealed many faces and played many roles - a thief, a mistress, an adulteress, a feminist, a selectively devout Catholic - and by the end of season four she plays estranged wife and part time co-conspirator to one of the most prolific bootleggers in America.
"I think out of all the characters, Margaret's circumstances have certainly been the most dramatically altered over the series," Macdonald says.
"Over the series, Margaret had real struggles with Nucky, her daughter gets polio, she falls in love outside of her marriage. She's gone through a lot."
Margaret's story is just as dramatic before the show started. After falling pregnant to her employer's son, she stole her mother's savings and moved from Ireland to America. On the journey over, she miscarried. Upon arriving in America she married Hans Schroeder, an abusive and alcoholic German immigrant.
Despite a life time of hardship, Margaret has shown herself to be a survivor above all else.
"I love her strength and her ability when times are tough to really look after herself and the people she cares for," Macdonald says.
Terence Winter, who is the creator, writer and executive producer of the show, is also fond of Margaret.
"Margaret is one of the most interesting characters for me and always has been. Here's this woman who on the face of it looks like a victim and she is a victim in many ways but she's also very strong," he says.
"Early in the series, Margaret gets a job in a dress shop and she steals a piece of lingerie and Kelly Macdonald called me and said, 'What am I doing? Is this Margaret?' and I said 'Yeah this is Margaret! Don't forget you're an immigrant woman who came to this country alone and you're married and somehow figured out a way to get yourself in a chair across from the most powerful man in the city.' There is a lot more to this woman than meets the eye."
Macdonald agrees, "She's the type of lady that when she's old and in her rocking chair her grandkids will listen to her stories, write them down ... and make a television show!"
Who: Kelly Macdonald
What: Boardwalk Empire, fifth and final season
When and where: Starts tonight: SoHo, 8.30pm
