Downton Abbey Season 4 spoilers, cast news: Paul Giamatti's start date schedule - to premiere at Christmas alongside Shirley MacLaine

Downton Abbey Season 4 is eagerly anticipated by fans, and new spoilers and cast rumors are emerging concerning the upcoming season.

In recent news it has been confirmed that Oscar-nominated US actor Paul Giamatti is to join the cast of the hit ITV show. He will join the cast on the Christmas episode, and should be a great addition to the show.

Giamatti will star alongside Elizabeth McGovern as Harold, the brother of Lady Grantham.

Other cast rumors suggest that Dame Kiri Te Kanawa and actor Nigel Harman will appear in the 4th season of the hit TV show.

Gareth Neame, from production company Carnival Films, has said, "We're excited that Paul Giamatti will be joining us on Downton to play Cora's brother Harold, the rather free-spirited uncle to Mary and Edith."

He added, "We can't wait to see him work alongside Shirley MacLaine, who are both sure to upset the Granthams' apple cart in this year's Christmas Day episode."

The British-American drama has become hugely popular in the United States, and this is being reflected in the many new additions of American actors.

According to the BBC, 12.3 million Americans watched the finale of Season 3 on 17 February – that broke the viewership record for broadcaster PBS.

Giamatti is an established actor, having starred in numerous Hollywood movies, as well as winning Emmy and Golden Globe awards for his role as former US president John Adams.

He is currently filming The Amazing Spider-Man 2, where he is playing The Rhino.