Lena Headey has handed a judge a letter from a Game Of Thrones producer as part of her child custody battle with her ex-husband.

The actress moved back to the native Britain with her six-year-old son Wylie and daughter over the summer (16) and the boy's father Peter Loughran went to court claiming she had violated their custody agreement by enrolling Wylie in a school without his permission.

Her ex was victorious in court as a judge sided with him and ordered her to bring the boy back to the U.S. once she's finished filming the TV show and to pay for Peter's travel expenses when he visits.

Lena has now supplied the judge with a letter from the series' executive producer Bernadette Caulfield which states she is needed in the U.K. until February (17).

The letter, obtained by TMZ.com, reads, "Dear Lena, This is a notification to confirm that you must be available in November and December 2016 for the filming and throughout January for possible additional scenes and pick-ups.

"As you are well aware, we are shooting through February 2017. Hopefully you will not be required past January 31st."

Lena also says she is paying Peter $10,000 a month in child support but he hasn't seen Wylie in the last three months.

A lawyer for the actress previously stated she wasn't breaking any custody agreement because she had planned to move to Britain with Peter, but he changed his mind. She had allegedly been hoping to keep her son in England permanently as she believes the education system in the U.K. is better than in America.

The former couple split in 2011 after four years of marriage, but only finalized their divorce in 2013 after a lengthy disagreement over custody and finances. The 43-year-old welcomed her second child in July, 2015, but has yet to reveal the little girl's name or the identity of her father.