Patricia Hodge will appear in the final ever episode of Downton Abbey.
The Miranda actress will join the cast for the conclusion of the period drama on Christmas Day.
Everything we know about the final series of Downton Abbey - and plans for the future
However, it is currently unknown who Hodge will play and whether she'll be spending her time upstairs or downstairs.
Earlier this week, the cast of the ITV hit reunited for a special BAFTA event honouring the series.
At the event, creator Julian Fellowes teased that there may be "some afterlife" for the show and its characters.
There has been a great deal of speculation that Downton Abbey could head to the big screen following its farewell series, but executive producer Gareth Neame has insisted that there are no immediate plans yet.
Meanwhile, Maggie Smith has admitted that she is "surprised" to have made it through to the end of the drama.
Downton Abbey is expected to return to ITV for its final series next month. Season six will begin in the US on PBS on January 3.
