Ovenden has been cast as aristocrat Charles Blake. Also joining the series are Tom Cullen as Lord Gillingham, an old family friend of the Crawleys who visits the family as a guest for a house party; Nigel Harman as Green, a valet; Dame Harriet Walter as Lady Shackleton, an old friend of the Dowager; Joanne David in a guest role as the Duchess of Yeovil; and Dame Kiri Te Kanawa as a guest who sings in the house.
"The addition of these characters can only mean more delicious drama — which is what 'Downton Abbey' is all about," said Masterpiece executive producer Rebecca Eaton in a statement.
Actress Shirley MacLaine (The Pajama Game, Me and Juliet) will also return to the show for next season's finale. She will reprise her role as Martha Levinson.
"Downton Abbey" is written and created by Julian Fellowes. Gareth Neame and Fellowes are executive producers. For more on the series, click here.