Movie star joins Downton Abbey cast

After the death of her husband Matthew, Lady Mary has been left holding the baby. Photo / PBS/Masterpiece

Emmy winning actor Paul Giamatti is joining the cast of Downton Abbey for the show's highly anticipated fourth season.

Network PBS confirmed the Sideways star would appear in the fourth season's "dramatic climax" as Cora's maverick playboy brother Harold.

Other stars joining the fourth season, which begins screening in the UK in September, include Kiwi opera star Dame Kiri Te Kanawa, Dame Harriet Walter, Tom Cullen, Joanna David and Nigel Harman.

Executive producer Gareth Neame said he was "thrilled" to welcome new faces to the hit period drama.

"Downton Abbey has seen many great characters visit the house over the years and we couldn't be more thrilled to welcome the new faces that will be joining the regular cast of Downton Abbey in Season 4.

"We hope audiences will be as excited about them as we are."

Kiwi fans will be waiting to see how Lady Mary copes with the death of her husband Matthew in a car accident, which ocurred on the same day as she gave birth to Downton's new heir.

It came at the controversial end of the show's Christmas Special.

Downton Abbey screens on Prime in New Zealand.

- nzherald.co.nz