Credit: WENN/PBS Photo: Shirley MacLaine Joins Downton Abbey

The Brits had better hold onto their hats: Downton Abbey season 3's American invasion has begun!

The first of the incoming tide will be Shirley MacLaine, who has been cast as Martha Levinson, the mother of Lady Grantham (Elizabeth McGovern).

"My late grandfather directed Shirley MacLaine in Gambit in 1966 so it is a delight for me that she will be joining us on Downton Abbey," said executive producer Gareth Neame in a statement. 

We can already picture the battle of wills between MacLaine and Dame Maggie Smith (the Dowager Countess)! Bystanders might want to flee while they can.

Downton Abbey's third season will continue shooting next month and is set to premiere in the United Kingdom in the fall. Then, it will likely air on PBS in early 2013.

Meanwhile, season 2, which is still airing in the U.S., will bow with a finale on February 19.