We are all familiar with the love story between King Edward VIII and American divorcée Wallis Simpson, which is considered one of the real-life love stories for the ages, as Edward abdicated the throne of England in order to marry his true love.

There is another great love story of the 20th Century, one not often told, between a king and a woman not considered appropriate to be his wife that took place about a decade later: King Seretse Khama of Botswana and the very British — and white — Ruth Williams.

Their forbidden love story is now being told in A United Kingdom, as Khama (David Oyelowo) puts his country and rule in jeopardy to marry Ruth Williams (Rosamund Pike), the woman he loved and needed by his side to rule. Their 1948 marriage caused an international uproar, and faced opposition from the British government, as well as the Khama family, but in the end, the couple triumphed over every obstacle and changed the course of African history.

“At that time apartheid had literally just been legalized in South Africa, and Botswana sits directly above South Africa; they share a border,” Oyelowo tells Parade.com. “So, if you are making it legal that black and white people should be kept completely separate, and then across the border, you have the incoming new king married to a white woman, that is not going to support your agenda. So, that’s why South Africa frowned upon the marriage to the degree that they did.”

In our conversation with Oyelowo, he also explains why we haven’t heard this love story, how Khama and Ruth improved life in Botswana, how difficult it was to get the movie made, and more.

It seems as if this should be a love story for the ages, like Romeo and Juliet, with a happier ending. Why haven’t we heard about it before this movie?

That’s a good question, and it’s exactly why I felt strongly about it being made. I think it’s because you see some pretty reprehensible governmental behavior in this story. So therefore, it’s not one that, certainly, was about to be trumpeted by the British government, nor the South African culture. And in Botswana, it very much got buried by a colonialist attitude, which is that everything that was done when there was a British protectorate is to be espoused, and the things that came after are not necessarily as significant.

So, when you go to Botswana, educationally, they know more about [Scottish explorer] David Livingstone than they even do Seretse Khama, and you find this happening time and time again. I absolutely found it to be the case when I played Dr. Martin Luther King in Selma that far less people than should be the case knew enough about the civil rights movement and the legacy of Dr. King, because educationally, they had been short-changed. So, those were reasons why telling the story was very important to me.

A United Kingdom (Twentieth Century Fox Home Entertainment)

What surprised me about their love story is that they were allowed to date at all, considering the time period.

This is a nuance that, certainly in America, people may not be aware of, but there wasn’t segregation in the U.K. like there was here in any sphere of life. So, people were allowed to associate with each other. But that doesn’t mean there wasn’t very overt and real racism. Yes, it may have been legally permissible, but it doesn’t mean that their relationship wasn’t frowned upon and that any fraternization between the races was something that was socially acceptable. But it was legally acceptable, which is why they were free to date and to be together.

But once it became official as a marriage, especially in relation to who he was politically, that’s when, especially in relations with South Africa, Great Britain felt the need to intervene, because they very much needed South African resources to fight the Cold War and to keep South Africa in the Commonwealth.

This is scripted, so how close to the truth is it?

It’s a movie, so you’re fitting a lot into two hours. But by and large, this is what actually happened. It’s a true story, and fairly faithfully told. We had members of the family as consultants for us through the film. We were very careful to make sure we shot the film largely in the places where the events took place both in terms of Botswana and the U.K., in fact, to the point where we shot in the very house that Ruth and Seretse lived. Rosamund Pike, as seen in the film, gave birth in the very hospital where Ruth Williams gave birth in real life. So, we went to great lengths to make sure that the story was truthfully told.

Why do you think the king didn’t walk away from Ruth? Was his love for her greater than his love for his country?

The truth of the matter is that he loved both Ruth and his country, and felt very strongly that they shouldn’t and didn’t have to be mutually exclusive. Others felt differently. The love that he had for his wife ended up being not only the force that kept them together, but went on to change that nation for the better forever.

I don’t think that they could have foreseen that their marriage would be the means by which Botswana would gain its independence, the means by which Botswana would be a country that, to this day, doesn’t recognize race, the means beyond which Botswana is now the oldest democracy in Africa, and also Africa’s greatest success story in relation to how much of its resources it controls, juxtaposed with other African countries. These were all byproducts of sticking to what they believed.

So, you can question whether it was right for him to jeopardize his leadership role for his love, but you could also argue that it was the right thing to do when you look at the byproducts of that.

Khama seems to be a man with quite a vision. His son, Ian Khama, is the current president of Botswana. Did you get a chance to meet him?

Yes, very much so. He visited the set, and Rosamund and I had the huge privilege of him looking at us depicting his parents and him saying, “I never thought I would see my parents again,” which was a huge moment for us.

I understand this was a passion project for you. How hard was it to get this movie made?

It was pretty tough, but one of the main reasons it was so tough is that I was determined, from day one, that I would be the one to get to play Seretse Khama. I first happened upon the book, The Colour Bar, that our film is based on, in 2010. That was before some of my more well-known starring roles, and it transpired that I was the one who was most enthusiastic about me playing Seretse Khama above everyone else, and it was going to take a few more opportunities in front of the camera before we could raise the financing for me to get to play this role.

So, that was a challenge, but I think sometimes the longer, certainly, a film like this takes to come to fruition, it just gives you more opportunity to hone the story and, hopefully, find the right auspices for getting the film made.

It’s really important to tell these stories like this and like last year’s Loving because they’re stories that illustrate that people, no matter what color, are intrinsically the same.

Yeah, I think that’s the power of cinema, that it can remind us, and show us of how much more alike we are than different, and how perception isn’t necessarily reality. Sometimes it takes two hours, or if it’s a great miniseries, a few more hours, of looking behind the veil of people who may be very different from you, or from a different culture or country than you, to recognize how many things we have in common. Movies and the media are a very, very powerful cultural tool, and sometimes they are used to keep people in ignorance or misinform them. So, any opportunity to address the balance of that, I think, it needs to be taken.

What are you going to do next?

I’ve done a couple of films that are coming out soon that are very different from A United Kingdom. One is a sci-fi film that’s part of the Cloverfield anthology, produced by J. J. Abrams and directed by Julius Onah, and that comes out October 27th. Also, I just did an action-comedy called Gringo that will be coming out next March 9th, and that’s a very, very different side to me, [playing a character] being chased across Mexico having made some very bad decisions.

It seems like you have a lot more choices now. Do you think that it was Selma that was the turning point?

Indisputably, Selma was a turning point for me. I don’t think A United Kingdom would have gotten made without the notoriety and continual growth from a notoriety point of view of that film. To be a “leading man” is a very privileged space to occupy, and not many actors are afforded that. Selma, definitely, was a turning point for me in relation to that, and I’ve continued to reap the benefits of it.

A United Kingdom is currently available on Digital HD, Blu-ray and DVD from Twentieth Century Fox Home Entertainment.