On 20 September, 1948, the regent of Bechuanaland’s dominant Bamangwato tribe received a letter that was to change the course of history. His nephew, Seretse Khama, the young king in waiting, wrote from his studies in England that he was to marry in a fortnight’s time: “I realise that this matter may not please you,” Khama admitted, “because the tribe will not like it as the person I am marrying is a white woman.”

Read more about this film: A United Kingdom: how a forbidden romance changed a continent | A United Kingdom film | The Guardian