Paul Giamatti for Downton Abbey Christmas episode

Paul Giamatti to join Downton Abbey

US actor Paul Giamatti arrives on the red carpet for the premiere of the film "Fred Claus," 03 November 2007 at the Graumanï¿?ï¿?ï¿?s Chinese Theatre in Hollywood, California.  Fake snow was falling on the red carpet for the event.  AFP PHOTO / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

Carnival Films and ITV have announced Sideways actor Paul Giamatti is to join the cast of Downton Abbey, alongside the return of Shirley MacLaine as Martha Levinson for the dramatic climax to Series 4.

The fourth series will see the return of series regulars Hugh Bonneville, Maggie Smith, Michelle Dockery and Jim Carter, with the Emmy, Golden Globe and SAG award winner Giamatti (John Adams, Sideways, Barney’s Version, Cinderella Man) playing Cora’s maverick, playboy brother Harold in the Christmas episode.

Carnival Films’ Managing Director, Gareth Neame 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.  We can’t wait to see him work alongside Shirley Maclaine, who are both sure to upset the Grantham’s apple cart in this year’s Christmas Day episode.”

Earlier in the year Dame Kiri Te Kanawa, Tom Cullen, Julian Ovenden, Nigel Harman, Joanna David and Gary Carr were also announced to star in the fourth series.

The drama is a Carnival/MASTERPIECE (NBC Universal) Co-Production, executive produced by Gareth Neame, Julian Fellowes and Liz Trubridge.

Downton Abbey will return in the Autumn.