Series four will comprise eight hour-long episodes plus an extended Christmas special

ITV has confirmed that Downton Abbey will return later this month (September).

The first episode of series four will air at 9pm on Sunday, September 22 following an episode of The X Factor. A further seven episodes will air over the autumn before the show rounds off its 2013 run with an extra-long Christmas special on December 25.

Earlier this month ITV unveiled a trailer for the new series – watch it below. The one-minute teaser shows Michelle Dockery‘s Lady Mary mourning the loss of husband Matthew, who died in a car crash at the end of the last series. It also features glimpses of new characters played by former EastEnders actor Nigel Harman, Black Mirror‘s Tom Cullen and Gary Carr, who plays the show’s first black character, a jazz singer named Jack Ross.

Meanwhile, Sideways star Paul Giamatti will also make an appearance during the new series, playing a maverick American playboy, as will Shirley MacLaine, reprising her role as outspoken relative Martha Levinson. Maggie Smith, Hugh Bonneville and Elizabeth McGovern will all be back as members of the aristocratic Grantham family.

Created and written by Julian Fellowes (pictured above right with Bonneville and McGovern), Downton Abbey premiered on ITV1 in 2010 and has gone on to become a major international smash. Over 120 million viewers worldwide are now estimated to have watched the show and Smith has collected two Emmy awards and a Golden Globe for her performance as the sharp-tongued Dowager Countess.