PBS announced that it will crank up the number of hours of programming it will devote in 2015 to its thriving British drama and mystery franchise “Masterpiece.”

Writing in The New York Times, Elizabeth Jensen reports that PBS will add at least 20 hours of “Masterpiece” programming during the year, representing about a 50% increase.

The extra hours will begin in January, when PBS airs a six-part “Masterpiece” mystery called “Granchester,” which will air after new episodes of “Downton Abbey.” In April, the franchise will air “Wolf Hall,” based on two Hilary Mantel novels, and other new projects will air later in the year, the story adds.

The programming boost comes after the success of “Downton Abbey” and “Sherlock,” which have helped more than double “Masterpiece’s” audience since 2010, Jensen writes.

She adds: “In 2014, new episodes of ‘Masterpiece,’ through September, are drawing an average 6.4 million viewers weekly; for the same period in 2010, new episodes averaged 2.8 million viewers, ‘Masterpiece’ said.”

“How often does this happen to a television series that’s 43 years old, to grow, to be expanded?” Rebecca Eaton, the program’s executive producer, told The Times.

The extra programming will come with additional corporate support. The new shows will have exclusive corporate sponsorship from Viking River Cruises, which has supported the program since 2011. From 2004 through 2011, “Masterpiece” had only “a handful of intermittent short-term corporate sponsors,” Jensen notes.

ExxonMobil ended its annual $9 million support in 2004.

Viking River Cruises Senior Vice President for Marketing Richard Marnell told The Times that sponsoring “Masterpiece” had helped boost awareness of the company, and that when the broadcast asked about supporting additional hours, “We immediately said yes.”