Regal role: Glenda Jackson plays the ageing Queen in Elizabeth R 1971. She is set to return to acting to play King Lear in October after 25 years

Glenda Jackson will make a dramatic return to the theatre after an absence of more than a quarter of a century – during which time, as a Labour MP, the House of Commons was her stage – to play Shakespeare’s tragic King Lear.

It’s a mouthwatering bit of gender-blind casting.

The double Oscar-winner will take to the boards of the Old Vic theatre in October, and said she was excited to be tackling the Bard’s most challenging work.

Jackson left acting in 1990, at the height of her powers, and made her maiden speech to Parliament two years later, after being elected to represent Hampstead and Kilburn in North London.

She stepped down from professional politics at last May’s General Election and within months was playing a 104-year-old character in an Emile Zola tale on BBC Radio 4.

Last night renowned director Deborah Warner, who will direct the 79-year-old Jackson, disclosed that she will start rehearsals in late August. Performance dates will be announced in April.

I have not been able to find another instance of a major, world-class thespian returning to the theatre after such a long time away from the footlights.

‘It is very exciting – biblical, really,’ director Warner said. ‘Who else has done that?! Who else has done that in any art, in any medium?’

Warner revealed she met Jackson just before Christmas to discuss what was then merely the possibility of tackling Shakespeare’s tragedy. ‘The fact that Glenda Jackson was excited about doing anything was overwhelmingly exciting,’ she laughed.

She added that having directed the play twice before – a celebrated production for the Kick theatre troupe that played at the Edinburgh Festival and the Almeida Theatre in 1985, followed five years later by a version at the National Theatre – she found the prospect of staging a third Lear ‘dismaying’. But that was before she met with Jackson.

Jackson did not want to discuss details of the production now, but promised she would talk about her new project later. However, Warner, speaking from New York, filled in some of the gaps for me.

She said Jackson had seen her great friend, the Spanish actress Nuria Espert, play Lear in Barcelona 13 months ago. ‘Seeing her do it must have been the trigger,’ Warner surmised.

I wondered how Jackson would tackle the part: In a role reversal as a woman, or strictly straight? ‘I think she’s playing Lear, full stop,’ Warner said. ‘He, or she, who takes the words into their mouth of any Shakespearian character, becomes the character. Boom. Done.’

Ms Jackson won two Oscars for her roles in movies Women In Love and A Touch Of Class during the 1970s

Second career: The actress went into politics as a Labour MP at the 1992 General Election before quitting in 2015. She has since had a role in a Radio 4 play

The director insisted that the production is not ‘an exploration of gender’. She did grant that there may be other bits of gender-blind casting, but she said she hadn’t made a decision on it, yet.

Before her years as an MP, Jackson inspired generations of actresses with performances in plays such as Strange Interlude and Mother Courage (as well as her collaborations with the visionary Peter Brook); her title role in the BBC drama series Elizabeth R; and her movies Women In Love and A Touch Of Class, which won her Academy Awards.

Her Lear will attract theatregoers and thespians alike – even those who don’t share her politics.

Some have criticised her as humourless, but that is not the case. She’s always acknowledged that she won her part in A Touch Of Class after being spotted in the Antony and Cleopatra sketch on the Morecambe And Wise show.

It reminded me to ask Warner to consider how Jackson’s Lear would match up against her Hamlet... I’m talking about Ernie Wise’s version, which she performed on the comedy duo’s 1979 Christmas special.

‘Hopefully, very well,’ she responded, with an almost straight face.