Ms. Jackson — with a helmet of cropped coppery hair, no visible makeup and a black and white dress from Marks & Spencer — roared right back at her audience. “Oh, c’mon,” she said, in the manner of a popular but stern school head on games day. “We don’t do standing ovations in England.”

For once, though, a standing ovation seemed warranted. Though Ms. Jackson holds a special place in the hearts of film and theater cognoscenti, she hadn’t exercised her acting muscles — or even attended the theater — during her years in Parliament. Yet critics had waxed ecstatic over her portrait of a despot suddenly betrayed by age — a man, as Ms. Jackson described him, to whom “no one had said ‘no’ in his entire life.”

“She appeared naked in a sense from her first entrance,” said Matthew Warchus, the Old Vic’s artistic director, who had facilitated Ms. Jackson’s return to her former profession. “We hadn’t seen her in so long, so it was an incredible thing to hear her voice again. That’s a neat trick, to make your first entrance after 20 years of silence.”

The ‘Antisocial Socialist’

In person, Ms. Jackson is formidable but hardly as forbidding as her reputation would have it. She answers questions with a conscientious courtesy, only slightly underscored by impatience. Her face remains the face she was born with, scored with the lines you would expect a lifelong smoker to accumulate but untouched by the mask-like distortions of plastic surgery.

On the morning I met her in London, she arrived at the cafe, straight from “bloody public transport,” in a sharp and purposeful blur, like a blade flung by a circus thrower seeking its target. She was again sans makeup and wearing drop pearl earrings (a gift from her son) and a wardrobe — red coat, black pants, buffalo check flannel shirt, running shoes — largely acquired from her trusty Marks & Spencer. (“A good thing about Marks & Spencer, they don’t hound you when you’re going round.”)

She was conscious of the time, since she was on “grandson patrol” that day and would be needing to pick up her son’s 11-year-old from school. At a certain point, she realized it might be a good idea if she had something to eat. We both ordered the soup, which came with bread.

“How big is the bread?” she asked the server. “It’s half a loaf isn’t it? One of those should do. One to share. Save money and save food. Two-thirds of the world go to bed hungry every night, and we stuff ourselves.”