DCI Vera Stanhope is to "investigate a murder" at Downton Abbey as part of a Text Santa special.

Hugh Bonneville in the Downton Abbey Text Santa special

Hugh Bonneville in the Downton Abbey Text Santa special

'Vera' actress Brenda Blethyn will bring her famous role to the hit period drama in a hilarious sketch in which she will inform Robert Crawley, Earl of Grantham (Hugh Bonneville) and Isobel Crawley (Penelope Wilton) that a crime has been committed at the house.

A clip of the special sees Robert and Isobel holding auditions for a Father Christmas for the Abbey before Vera stumbles in announcing herself as DCI Stanhope of Northumberland and City police, adding that she's there "to investigate the murder".

Lord Grantham is quick to insist that "there hasn't been a murder".

However, the DCI points out: "It's a stately home, there's always been a murder."

Brendan Coyle's character, butler Mr. Bates - who is known by fans to have had a number of run-ins with the law - then appears out of nowhere before announcing that he thinks he may have left an iron switched on somewhere in the house.

Vera begins to hand out instructions, shouting: "Nobody leaves the room... except you pet, go see to that iron."

Former 'Strictly Come Dancing' host Sir Bruce Forsyth is also expected to appear in the one-off special.

The full sketch will air on Text Santa Christmas Jumper Day on December 18 at 8pm on ITV.