A producer on Spencer, an upcoming film about Princess Diana, has insisted there isn't ban on British actors playing Prince William, despite a casting call suggesting otherwise.

It was announced in June that Kristen Stewart will be playing the late Princess of Wales in Pablo Larrain's Spencer, which will be set across three days during one of Diana's final Christmas holidays in the early '90s and will focus on her deciding to end her marriage to Prince Charles.

Ahead of the film's shoot in Germany early next year, a casting call for the role of 11-year-old William, Diana and Charles' eldest son, was posted online on Thursday. It noted that British actors shouldn't apply for the part of the British royal "due to new Brexit rules from January 1st 2021", when the U.K. is due to leave the European Union.

However, Spencer producer Paul Webster has insisted to Deadline that British actors are being met for the part and Brexit is not an hindrance on casting.

"We're meeting British boys all the time for this role," he said. "If they happen to have an Irish passport all well and good. But it's not a hindrance to have a British passport. We're not saying we need a foreigner to play Prince William.

"Many of our cast will be British. Some of our cast will be European to meet certain funding requirements. But this is an official co-production with Europe so we don't anticipate any issue with our British cast working in Germany. There is no connection to Brexit."

A representative for the British Film Institute (BFI) confirmed to the publication that despite there being no post-Brexit agreement between the U.K. and European Union, certain U.K. and European co-productions with a British cast are expected to be able to shoot on the continent due to the Council of Europe Convention on Cinematographic Co-production.