When Scarlett Johansson walks into the room, it's difficult not to sneak a peek at her stomach.
Most of the world is on "bump watch" amid rumours that the Hollywood star is pregnant with her first child. The 29-year-old, who's engaged to Frenchman Romain Dauriac, takes it all in her stride when asked about the global focus on that part of her anatomy.
"Oh, all different parts of my body have been stared at. I'm used to it," says Johansson in that husky intonation which she recently used to great effect as the voice of a computer system in sci-fi romance Her.
In the flesh, Johansson's features are doll-like – even the famous pout isn't as pronounced as it seems on screen.
Dressed in jeans, a floaty polka dot top and black jacket, there's no telling if she's concealing a baby bump.
If she is, you wonder if this modern-day screen siren might be cast differently in the future.
"I don't know," she ponders. "I've been in the industry for 20 years and the roles that become available to me change as I grow older and transition through life. You hope to have a career that has longevity and reflects the experiences you've had. It's what we all hope for, men and women alike."
A New York native, Johansson made her stage debut as an eight-year-old child in an off-Broadway production with Ethan Hawke. Film roles followed, including Rob Reiner's comedy North and the thriller Just Cause, with Sean Connery, before she achieved worldwide recognition as a traumatised teen in Robert Redford's The Horse Whisperer.
She recently reunited with the acting legend in the latest Marvel Comics offering, Captain America: The Winter Soldier, a sequel to 2011's Captain America: The First Avenger which followed the creation of the "world's greatest soldier" (Chris Evans) back in the 1940s.
"It was wonderful working with Robert Redford," she says. "It was nice to speak to him about adult things – politics, activism and work and just to catch up."
The action blockbuster sees Johansson return to the role of Natasha Romanoff, aka Black Widow, for a third time as part of the greater Marvel Studios world which also encompasses the Thor, Iron Man and Avengers movies.
"It's an interesting challenge to keep coming back to this character, and I have the good fortune of playing someone evolving with each installment," she says of the skilled assassin.
She'd just finished the Broadway run of Cat On A Hot Tin Roof before shooting the movie last year.
"Broadway's pretty much the most physically challenging thing you can do, and if anything was going to prepare me to have stamina it was that," she says.
As for getting ready to wear Black Widow's catsuit, the process is "boring", she insists. "I get up at 5am, go to the gym, train like a dude and then eat a bunch of lettuce. It's not glamourous at all."
While Black Widow might not possess powers like her fellow superheroes, she isn't someone to mess with.
"She has to be quick-thinking and her fighting style is to use her size to her advantage," says the 5ft 3in actress. "She's fighting these huge guys, so it's like a Tom and Jerry situation, but it's what makes the character so playful."
As for her being a role model? "I'm not sure," says Johansson. "Let's not forget, she started out her career essentially as a mercenary. But she doesn't rely on her sexuality or physical appeal to get the job done. She's extremely smart, she thinks on her feet, she's a leader and I think she has a lot of foresight.
"Those are all qualities to celebrate for young women."
The film's themes involve trust, with the characters questioning who they can rely on and how freedom and privacy are being infringed upon.
The actress understands the potential implications in the modern world. In 2012, Christopher Chaney was sentenced to 10 years for hacking the computers of celebrities, including Johansson's (nude photos she'd sent to her then-husband Ryan Reynolds were splashed on the internet).
Was she satisfied with Chaney's sentence? "Yeah," she says, adding with a wave of her hand: "That's old news!"
She considers herself pretty trusting. "I guess I wait for people to prove me wrong and then I don't trust them after that."
It must be a tricky topic when you're one of the world's most famous women.
"There are things about being in the public eye and media which are sh**ty and annoying," she says, before starting to laugh. "Oh, that sounds really eloquent!
This November, she'll turn 30. "I'm not there yet, don't rush me," she jokes. "It's funny, because I actually have a twin brother [Hunter] and sometimes I look at him and go, 'I can't believe you're turning 30'!"
She's looking to be challenged more, though. Her recent role as an alien seductress scouring Scotland for lone men in the haunting Under The Skin would attest to that.
"It's nice to grow. I never get hung up in one corner," she says.
CAPTAIN AMERICA: THE WINTER SOLDIER IS RELEASED ON FRIDAY