Chris Bryant fleshes out the story. Aged three when war broke out, Jackson grew up in a family run by strong women while the men were away fighting. At 16, she went to work in Boots before her successful Rada audition, and an acting career at first hampered by her conviction that she was ugly.
Then, in 1963, she met Peter Brook, and starred in his Theatre of Cruelty season. Her mesmerising performance as a cataleptic Charlotte Corday in The Marat/ Sade led to roles that gave her iconic status in the Sixties and early Seventies. She never balked at taking her kit off (there's a tale about her swinging from the ceiling during school showers). Her nude scenes in Ken Russell's Women in Love and The Music Lovers became symbols of the era's fascination with marriages of sexuality and madness.
Other films, such as Sunday, Bloody Sunday and A Touch of Class, are reminders of Jackson's characteristic mix of strong feminism and traditional morality. Television series such as Elizabeth R showed off her autocratic tendencies, and The Morecambe and Wise Show revealed a comic side to her talent. On stage, her roles - including The Maids and Hedda Gabler, The House of Bernarda Alba and Mother Courage - secured a large following.
So why did Jackson give up acting in 1991? Her detractors say it's because she reached the end of the road - they see her as overrated, dictatorial and losing inspiration. In her defence, Bryant praises her audacity, her ability to delve into the darker recesses of the human psyche, her commitment, and her unforgettable "cracked bell of a voice", which can "pour honey or spill razor blades".
Bryant concludes Jackson swapped careers as "she wanted to do something more useful than act". Again, her moral upbringing dictated her choice. Haunted by a deep feeling that she ought to be doing something socially useful, and motivated by her detestation of Margaret Thatcher, she became increasingly political in the "greed is good" decade. Apparently, she was so angry at Thatcher's "No such thing as society" speech, that she walked into a glass door.
Quitting the stage for the hustings inevitably led to comparisons between Westminster and the theatre. Jackson's quip is that the Commons "is under- rehearsed and badly lit, and the acoustics are terrible". More seriously, she sees both acting and politics as a quest for truth. But while actors need to let go of their egos, politicians tend to crave ego-massages. In her case, Labour got both Glenda the Glamorous, queen of the photo op, and Earnest Glenda, hardworking MP and, until July, junior minister responsible for London Transport, aviation and shipping.
The timing of this biography, and the fact that its author was part of Jackson's 1992 general election campaign team, suggests that the book has a wider purpose. Nagging suspicions are confirmed on the last page, where she steps out as a "keen and well-regarded candidate" for the job of the first directly elected mayor of London. There's even loose talk of a "dream ticket" of Jackson and Trevor Phillips.
If she does take part in the mayoral election, her parliamentary experience will be crucial. As the minister once responsible for the capital's overcrowded public transport, she would be at the centre of the campaign because, as the Culture Secretary Chris Smith argues, "The election'll be won or lost" on this issue. Perhaps. Equally, Londoners may blame her for government complacency in the face of a decayed and inefficient Tube system.
With its back-cover picture of "Red" Glenda, clasping hands with a grinning Frank Dobson above an eye-catching endorsement from Ken Livingstone ("She's the most right-wing minister the Labour Party ever had"), this biography is packaged as a campaigning aid. In contrast to Bryant's previous work - a serious tome on that most serious of Labour chancellors, Stafford Cripps - this is gossipy and politically lightweight. While not a hagiography - Bryant quotes nasty stories and bad reviews - neither is it particularly insightful. Its last paragraph leaves us with Jackson the truculent: "I'm going to be the most appalling old lady." Be our guest, Glenda, be our guest.
The reviewer's book `In-yer-face Theatre' is to be published by Faber next year