Production firm Carnival Films, part of NBCUniversal International Television Production, and U.K. broadcaster ITV said she would play Denker, Lady’s Maid to Violet, Dowager Countess of Grantham, portrayed by Maggie Smith.
Johnston also starred in BBC comedy The Royle Family and played a psychological profiler in BBC drama Waking the Dead.
Other guest actors for the new season of the period drama include Richard E. Grant, Anna Chancellor and Rade Sherbedzija. Also, Harriet Walter reprises her role as Lady Shackleton, and Peter Egan returns as Lord Flintshire.
Downton Abbey returns to ITV this fall. The fourth season brought the strongest ever season launch for the show. The season drew a consolidated average audience of 11.9 million.
Downton Abbey also hit a ratings high in the U.S. as the season 4 opener on Masterpiece on PBS averaged 15 millions viewers. The season made the show the highest-rating TV drama in PBS’s history, reaching over 26 million viewers.
The Carnival/Masterpiece co-production is executive produced by Gareth Neame, writer Julian Fellowes and Liz Trubridge.