A United Kingdom: the true story of Botswana's first president and the English woman he loved

He sent her images of Ruth and Seretse – ‘And she sent an email back saying they’d made her cry…’ ‘It’s true,’ says Pike, who is having her hair and make-up done next door. ‘He sent me an email with some photographs, and I was cooking dinner. I didn’t know anything about the story, didn’t know who these people were, but I had the most incredibly profound reaction to them. I started to cry, and I don’t know why. I still haven’t analysed why, but I just had this very visceral reaction.

‘Something touched me very deeply. Then I read the script and that feeling was borne out when I knew the story. ‘I never think about genres, but I do feel that in general cinema needs more love stories; people are not really making them. It’s one of the most deeply human things you can express on screen, and something that everybody can relate to – even if not in experience, in wish. We all aspire to love like this. And it’s also a journey from innocence to experience.’

Suddenly Oyelowo found he had both director and co-star, and things needed to happen very fast indeed. Six weeks of shooting in Botswana ensued, an unconventional decision because of the country’s lack of filmmaking infrastructure (most films set in Africa are shot in South Africa for this reason). The crew were determined to shoot in real locations, and to use as many local people as possible.

Auditions were held in the Lady Khama Community Hall in Serowe, and there were a few people in the cast of extras who had known Ruth. The crew also tracked down the Khamas’ original house in Serowe, abandoned and nearly derelict, and restored it for the film. They transformed a railway station in Palapye to fit the period; costumes were meticulously recreated.

The most poignant moment of filming, says Oyelowo, was when the president came to the set. ‘Meeting him was like a scene in a movie by itself. We were shooting in the middle of nowhere and we heard these helicopter blades and thought, oh, that’s blown the shoot. Then we were told that the president had just landed and was on his way to set. He watched Rosamund and Terry do a scene together and went from his stoic presidential self to… well, you could see something change in him and he actually said, “It’s my mother and my aunt,” and was very moved by it.’

Back in Botswana, the premiere of A United Kingdom is a huge success. It is an extraordinarily uplifting film, completely beautiful to look at, and moving without being slushy. During the screening there are shouts of joy when some of the audience recognise people they know on screen. At the end there is a standing ovation. ‘Pula!’ people shout approvingly. ‘Pula! Pula!’