BEVERLY HILLS, Calif. (AP) — PBS is standing firm against airing "Downton Abbey" simultaneously with the drama's U.K. season.

Despite the spoilers that leak online from its British run, the period drama has been a ratings hit for public TV, PBS chief executive Paula Kerger told the Television Critics Association on Tuesday.

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"You kind of don't want to mess with that if it's working so well," Kerger said.

Word-of-mouth from the British airing helps create buzz and promotion in advance of its PBS run, she said.

The show begins its fourth season in Britain this fall, with PBS airings starting Jan. 5. It picks up after last season's death of scion Matthew (Dan Stevens), heir to the English estate at the drama's center. Newcomers include Paul Giamatti as an American relation.

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Asked about rumors that the next season of "Sherlock" starring Benedict Cumberbatch might air at the same time in the United States and Britain, Kerger said the debut date has yet to be set.

The updated exploits of the Sherlock Holmes character has attracted the same "passion and enthusiasm" as "Downton," she said, so PBS is considering its scheduling very carefully.

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