Peter, who is the creator of Netflix's The Crown, and Gillian were together since 2016. They worked together on Season 4 of The Crown when the British-American actress took on the role of the U.K.'s first female prime minister, Margaret Thatcher.
Peter and Gillian were originally set up by Vanessa Kirby, who played Princess Margaret on The Crown's first two seasons. Vanessa introduced the pair when she was playing Stella Kowalski and Gillian was playing Blanche DuBois in A Streetcar Named Desire in London.
As of this writing, representatives for Peter and Gillian have declined to comment about reports of their split. The showrunner and actress have also not personally spoken out.
"We made a pact, actually, that we weren't going to talk about it at all," the X-Files alum replied when asked if Peter gave her feedback at home on her performance as Margaret Thatcher.
She continued, "I wasn't allowed to talk with him or express opinions about the scripts and he wasn't allowed to express opinions about my performance.
"Somehow, we managed to stick to it, which is unbelievable because neither of us can keep from expressing our opinions the rest of the time."
In interviews, Gillian had talked about quarantining together during the coronavirus pandemic, along with her children. She has a daughter, Piper, 26, from her first marriage to Canadian television art director Clyde Klotz. Additionally, Gillian has two boys at home: Oscar, 14, and Felix, 12, from a previous relationship with British businessman Mark Griffiths. Peter has five children from a previous relationship.
We wish Gillian, Peter and their family well during this time.