Downton Abbey cannot go on indefinitely, actress Penelope Wilton has said, despite the huge success of the period drama.
The star, 67, plays Isobel Crawley in the hit show which has enjoyed high ratings globally and is now in its fourth series.
But asked whether her character or Julian Fellowes' ITV drama had an indefinite shelf life, Penelope told the Radio Times: "I doubt it. I don't think anything can go on and on. Everyone would be bored stiff with it."
Penelope said of the cast, who include Dame Maggie Smith and Hugh Bonneville as well as guest stars Dame Kiri Te Kanawa and Shirley MacLaine: "We have a very close relationship, all of us, because we have worked over four years together.
"We've got to know each other very well professionally, so we do interact very well."
The former Doctor Who star added: "It is like being in a (theatre) company and all the better for it probably because you can talk in shorthand, as it were, and do more of the acting."
Penelope said that the long series shoot, from February to August, went by quickly thanks to the Downton cast's love of the Bananagrams word game.
"We play a lot of Bananagrams... We do very short scenes so we come in and out. We don't get bored with one another. It is the closest thing in television to being an ensemble in theatre."
Meanwhile, actress MyAnna Buring, who appeared in Downton as maid Edna, said she was not sure if her alter-ego would be back in the drama.
"I don't know, but never say never with Downton. I was such a massive fan of the show that sitting down at the kitchen table opposite Mrs Hughes and Carson was surreal," she told the magazine.
Asked whether she expected the rape scene involving house maid Anna Bates (Joanne Froggatt) to provoke such controversy, the Ripper Street actress said: "I think rape should always provoke a very strong reaction. It will be a sad state of affairs when it doesn't."
