Dame Maggie Smith is preparing to deliver her final acid put-down as the Dowager Countess in Downton Abbey.
She has told writer Julian Fellowes she wants the third series to be her last, although he has persuaded her to do the Christmas special.
The ITV drama, which is currently being filmed on location at Highclere Castle in Hampshire and at Ealing Studios in London, will return to ITV for the third time in September.
Fellowes has yet to complete the plot-line – but sources say he is preparing to write out the formidable Dowager Countess.
‘Maggie has asked Julian to write her character out,’ says a source. ‘She is filming until August and then wants to leave, going out on a high. She thinks that three series is enough and she wants to get back to the stage and big screen.’
The Dowager Countess is one of Downton’s best-loved characters and famous for her po-faced, one-line put-downs. My source says she is likely to be struck down by a fatal illness at the end of the third series.
Dame Maggie, 77, won an Oscar for playing a troubled teacher in the 1969 film The Prime Of Miss Jean Brodie. But she remains best known for her roles in Harry Potter and Gosford Park, the latter another Fellowes creation.
In November, she will return to the big screen with Michael Gambon in the BBC Films comedy, Quartet.
Last week it was reported that Dame Maggie has not renewed her contract.
The source added: ‘She is keen to pursue other roles so Julian is preparing to write her out. He always has several endings so it won’t be too difficult for him, but losing Maggie will be a great loss.’
In a TV interview, Fellowes admitted: ‘I can’t pretend it won’t be a knife in my heart when she decides to move on.’
Reports also suggest that Dan Stevens, who plays Matthew Crawley, has yet to renew his contract – prompting concern he may be the next to leave.
A spokesman for the show said: ‘Carnival Films don’t ever comment on future story lines.’