Glenda Jackson has made a "ferocious" and "magnetic" return to the stage after a 25-year break.
The Oscar-winning actress and former MP received glowing reviews for her lead performance in Shakespeare's King Lear.
Deborah Warner's modern-dress production opened at London's Old Vic on Friday night.
Its starry cast also includes Celia Imrie, Jane Horrocks and Rhys Ifans. The action mainly unfolds on a sparse set consisting of large white panels.
As the Fool, Notting Hill star Ifans wears a tattered Superman suit, sings like Bob Dylan, and, at one point, dons a scary clown mask.
In another scene, Ab Fab star Horrocks, as Lear's daughter Regan, playfully lobs an "eyeball" into the audience.
Jackson, 80, gave up acting for politics a quarter of a century ago and served as a Labour MP for Hampstead and Kilburn for 23 years, stepping down prior to the general election in 2015.
One of the biggest laughs of the night came after a line in the play about "scurvy politicians".
The Old Vic's artistic director Matthew Warchus said he felt "very honoured" that the actress had chosen to make her stage return in his theatre.
"I've asked her several times in the last 25 years if she'd be interested, but this time she was ready," he told the BBC.
"She came to me in the office and we walked on the stage together and she was primed and eager to come back.
"I asked her what she wanted to do and she said 'I want to play King Lear'.
He went on: "She's got that incredible voice. Obviously she's been using it as a politician so it's never lost any of its muscle."
The critics were largely in agreement.
The Guardian's Michael Billington said Jackson had ended her 25-year absence with "a ferocious, unflinching performance" that transcended gender.
"Jackson, like all the best Lears, shifts in a moment between madness and sanity, anger and tenderness, vocal force and physical frailty," he said.
"No ifs, no buts... she has pulled off one of those 11th-hour feats of human endeavour that will surely be talked about for years to come by those who see it."
Anne Treneman, in The Times, observed: "The cast is stellar and the brightest of all is Glenda Jackson".
"Thanks to its magnetic star this show is undeniably theatrical," Quentin Letts wrote in his Daily Mail review.
"Lear played by a woman? Daft, but you are forced to take notice. This is showbusiness, after all.
"She makes for a shrivelled Lear, lined as a walnut, scuttling, hobbling, flicking her unisex fringe and waving two distractingly large, washerwomanish hands as though in semaphore."
'Monster of a play'
Actress Celia Imrie, who plays Lear's scheming daughter Goneril, told the BBC she had known Jackson for 41 years having been her "tea-girl" on a tour of Hedda Gabler.
"It's wonderful that we know each other, especially as she says such horrible things to me during the course of the play," she said.
"What a way to come back," she added. "What is quite astonishing is that you don't have any doubt during the play that she is a king. I'm very proud to be in it."
She said rehearsals had been "quite full on" because "it's a monster of a play".
"Her brilliant power has never faltered since day one," she said, "and has never faltered from when I knew her 41 years ago."
Warchus added: "The Old Vic is a stage that's had a lot of great performance on it in its time and it was like watching a little piece of history being made tonight."
King Lear is at The Old Vic until 3 December