The title of season four, episode six of The Crown is “Terra Nullius,” a Latin phrase that means “nobody’s land.” Creator Peter Morgan no doubt picked it due to the presiding plotline: Charles and Diana’s 1983 royal tour of Australia, which coincides with the country’s growing movement to leave the British Commonwealth. Nearly 200 years earlier, Great Britain used the concept of “terra nullius” to justify colonizing Australia, claiming the land was unclaimed and unpopulated, despite its residing Aboriginal population.

But it also serves as a double entendre: Diana and Charles also find themselves in uncharted territory, a no man’s land. This is their first overseas tour together—and with the monarchy in a perilous position, a successful impression is paramount. Can they put aside their early marital problems, their clashing personalities, for the Crown? Or are they doomed to fail? While, for a brief moment, Morgan depicts the two sharing a moment of true connection, they are soon at odds again. After the tour is done, Charles takes a car back to their country home of Highgrove, whereas Princess Diana hightails it back to Kensington Palace in London. They never found common ground.

The episode chalks up their cracks to a multitude of factors: Diana’s supposed fragility—Charles gets frustrated that she can’t hike up Ayers Rock (now renamed Uluru) without stopping. The presence of Prince William—Diana wanted to bring him on tour and is anxious about their separation, much to the dismay of the royal courtiers and their strict schedules. Then, perhaps most of all, there’s Diana’s explosive popularity, which overshadows Charles’s: “This was supposed to be my tour! My tour as Prince of Wales to shore up a key country in the Commonwealth at a very delicate moment politically!” Josh O’Connor’s Charles screams at Emma Corrin’s Diana.

The Crown, at the end of the day, is historical fiction—the show takes real-life events and dramatizes them. So, in this hour-long tale of a very well-known couple, what’s fact, and what’s fiction?

It’s true that this was a politically sensitive tour: A wave of Republicanism was sweeping Australia, championed by its Prime Minister at the time, Robert Hawke. On March 6, 1983, a mere 12 days before Charles and Diana were set to fly to Australia, a television interviewer asked if Charles would make a good king of Australia. “I don’t think we will be talking about kings of Australia forever more,” he replied. Then he said he thought people would eventually vote to have a republic.