The Post is not just about journalists holding a government to account.

It is also the story of one woman - The Washington Post's late publisher, Katharine Graham, and her fight to be taken seriously by her male-dominated board of directors and news editor.

Meryl Streep, 68, who plays her, knows what it feels like to be dismissed, ignored and talked over by male colleagues, just as the film shows Mrs Graham was during meetings. "I don't know one woman who hasn't had that experience in a meeting," says the three-time Oscar winner (Kramer Vs. Kramer, 1979; Sophie's Choice, 1982; and The Iron Lady, 2011).

In a one-on-one chat with The Straits Times in New York last month, she says one way to improve gender equality is for women to help one another succeed, rather than compete among themselves.

She vividly remembers what gender dynamics were like in the 1970s. "The year this film takes place in, June 1971, was when I graduated from college. And I remember there were very few women in business, law and medicine... they were the outliers."

In newsrooms, "most women would be at work at entry-level positions in the newspaper".

"My friend Nora Ephron, to whom this film is dedicated, went to the offices of Newsweek," she says, referring to the late screenwriter who penned When Harry Met Sally (1989), Sleepless In Seattle (1993) and Silkwood (1983). "Katharine Graham, at the time, was the head of Newsweek and Nora applied to be a reporter, and they said, "Reporters are men. You could be a researcher, you could be an assistant, a secretary.

"And so the world was very different. And yet, even for all the in-roads we've made at the entry level, there are still very few Katharine Grahams, very few women in charge."

Asked what can be done about workplace inequality today, Streep says: "I think there's courage in numbers. The more you have in your cohort, the better off we are. So promote women, help other women.

"For a long time, when I was young, women would sort of keep each other out. They sort of liked being the only female in the room - that was a privileged position.

"And, actually, you have to realise that's not a privilege. It's a liability. Until you have critical mass, nobody's going to pay attention to you."

In the film, Mrs Graham - encouraged by editor Ben Bradlee (Tom Hanks) - has to decide whether to stand up to her board and the newspaper's lawyers, who were advising her not to publish leaked material about a government cover-up over the Vietnam War, because it could land her in jail and jeopardise the newspaper's financial standing.

This was not easy, especially given "how hard it was to be a woman in 1971 and be the head of a company", says the film's director, Steven Spielberg, in a separate interview. "When you sit in your boardroom with people who are ostensibly reporting to you, every man looks through you to the man sitting in the next chair. Katharine was invisible in a sea of men and she hadn't found the confidence to assert her authority.

"But her watershed moment comes in our story," says the film-maker, adding that he views The Post as a feminist film and is gratified to see echoes in today's #metoo movement, where women are speaking out against abuses of power by men.

Streep notes how far women have come since the 1970s, when there would be, for instance, only a few women with any power in The Washington Post's offices - "unless she owned the building and the paper like Katharine did".

But there is still a long way to go before the sexes are equal, says the star, whose more recent films include The Devil Wears Prada (2006) and Into The Woods (2014).

"There was a negotiation of how women lead and that evolved over time. And that's still changing and we're still getting to it, I think.

"We still need a new set of listening ears on the side of the men and we need to know how to assert ourselves as women," notes Streep, who is married to sculptor Don Gummer, 71, and has four children aged 26 to 38, including actresses Mamie and Grace Gummer.

Yet she is upbeat about the future. "I do think the world is changing, and that there are certain kinds of behaviours that men were not really aware they were enjoying.

"And there's going to be more inclusion at the top levels. That's what everybody is insisting on and I think it will happen.

"I'm optimistic. You feel the thing shifting. It could backslide again, like these things do. But we're two steps forward, one step back. That's the way progress will be made."