US actor Paul Giamatti is to join the cast of Downton Abbey, starting with the Christmas episode.
ITV announced he will star alongside as Harold, the "maverick, playboy" brother of Lady Grantham. played by Elizabeth McGovern.
Dame Kiri Te Kanawa and EastEnders actor Nigel Harman are also set to star in the fourth series of the period drama. Shirley MacLaine has already appeared.
The influx of US actors reflects its growing popularity in the States.
The BBC reports 12.3 million Americans watched the finale of series three in February, making it the highest-rated show of the day. The show has won nine Emmys.
Giamatti had supporting roles in films such as Saving Private Ryan and The Truman Show before a breakout role in Sideways.
In 2008, he won Emmy and Golden Globe awards for his performance in the title role of John Adams in a television series about the second president of the United States.
He was also nominated for a best supporting actor Oscar for his work in Cinderella Man in 2006.
