‘You get more confident as the parts run out’: Harriet Walter on her stage career, Succession and Shakespeare’s women

It has been simmering for years. Long before she was a dame, before she was withering in Succession, had appeared opposite Chewbacca in Star Wars, fat-shamed a baby in Ted Lasso and become one of the few – possibly the only – actor to play both a king and queen of England, Harriet Walter was Ophelia in Richard Eyre’s revelatory 1980 production of Hamlet (the one in which Hamlet ventriloquised the Ghost). Each night she watched from the wings as the prince and his mother had their heated debate: “Jill Bennett’s Gertrude was squirming under Jonathan Pryce’s blast. I used to think: ‘Oh Gertie, get a hold of yourself…’”

Now Walter has written an extraordinary book (her fifth) in which Gertrude, among others, has her say. In spiky Shakespearean verse. She Speaks! brilliantly creates secret lives and new monologues for 30 of Shakespeare’s women – including Anne Hathaway. Ophelia explains that she did not actually drown but faked her death with the help of the grave digger: she ran off to a nunnery and has been whooping it up with some wild sisters. Cleopatra is bored rigid, stuck in heaven with Antony: “Without command and sway and sexual sizzle/ It’s all one dreary democratic drizzle.” Lady Macbeth, who met the witches to suggest that her husband’s ambition needed a bit of a nudge, rhymes “nagger” with “dagger”. Desdemona, most miserably fading of heroines, conjures up the love she shared with Othello and concludes, beautifully and in anguished realisation, with lines that entwine Shakespeare’s own: “I just woke up as you put out my light.”

Distillation with a depth charge. On the page as on the stage, there is no slack or flummery, no breathy intensity with Walter. She is concentrated: the least fidgety person I have ever met. Almost completely still as she talks, and uncluttered: long and lean like a hieroglyph; dark brown top and trousers, creamy blouse; no bag! – though perhaps her actor husband, Guy Paul, with whom she is about to set off for Spain when we meet, is guarding it round the corner with her wheelie case.

She is also getting ready to play Margaret Thatcher, watching “acres of footage”, most of it for the first time, as in the 80s “I switched off when she came on”. She is not aiming at impersonation – “I think the closer you get to an imitation the less you really find out about the person” – but has been working on the voice and is beginning to find herself slipping automatically into the walk: “Basically, her head was always going first, and her feet catching up.” The result will be seen next year in Brian and Margaret, a Channel 4 drama written by James Graham – of telly’s Sherwood and the stage’s Dear England – and directed by Stephen Frears. Steve Coogan will play Brian Walden, Labour MP turned caustic interviewer: a notorious televised clash between him and Thatcher featured a comically charged dispute about who was the more domineering. Walter believes that “no one has seen the side of Margaret Thatcher that James Graham has brought out”. It goes against the grain, but “I’m beginning to understand her”.

Thatcher takes her place in the long queue of Walter characters who could never be called cuddly – though who would even see cuddly as a category if she were a man? The list includes Hedda Gabler, Killing Eve’s Dasha, Lady Macbeth, Ted Lasso’s Deborah, The Duchess of Malfi and Succession’s Lady Caroline Collingwood. Growing up in “the foothills of aristocracy”, in a “downwardly mobile” family who knew people with country piles but didn’t have a pile of their own, was good prep for performing icy composure and for observing what it might be like to be married to Logan Roy. Walter knew as a child what it was to be “on the receiving end of cold, snooty, put-down people”. Flippancy was at a premium and “no one said anything very serious” (I would love to see her in Noël Coward). When her father left the household he told his 13-year-old daughter: “I’m sure I can rely on you to take it like a chap.”

Walter’s new book might have been written to knock the snooties off their perch. It sprang from longstanding love and discontent. “Of all the parts I’ve played, the roles that have expressed me best have been Shakespeare’s. He accommodates anything that you want to say about being human. And yet there is this big gap, a lacuna where the woman’s point of view is not present.” When his characters are put in order of the number of lines they are given, only 15 women’s parts fall into the top 100: As You Like It’s Rosalind is highest placed at 15; Lady Macbeth comes in at 138. It is not, Walter thinks, that Shakespeare fails to understand women: he is simply telling stories where they are not at the centre. The women would all, of course, have been originally acted – shrilled and yelled – by boys, which opens up the possibility that a star performer could have progressed from playing Ophelia to being Hamlet. The title She Speaks! makes ironic play with Romeo’s apparent astonishment when Juliet opens her beak on what was, according to Walter, not really a balcony.

She has played 21 Shakespearean parts. To make sense of an underwritten role, “most of the time you are nursing a whole complicated subplot inside your head. It is very important that the actor has it, but it isn’t something that the audience can read clearly.” You can, though, sometimes get a glimmer: when Walter played Lady Macbeth, opposite Antony Sher, in Gregory Doran’s galvanic 1999 production, I remember feeling she was tracing a perfect arc as she glided from overprotective mate to valkyrie.

Once she started writing the speeches, words came “in a rush. I found things floating to the surface which had obviously been inside me for quite a while.” After four decades of speaking Shakespeare, the beat of his verse comes into her head “like music”. Here is a pulse with a practical purpose: it is not sugared phrases that enable Richard III to pull off his incredible seductions, but his ability to ensnare by the rhythm of his speech. Walter provides something for buffs too: deceiving echoes. Her Gertrude, who turns out to have been in love with Claudius since she was a slip of a thing, never did think much of Hamlet’s father. “He was a viper when he went to school/ At home he rampaged like a shackled bull.” That “viper” is lifted from one of the best ever theatrical quarrels – in A Midsummer Night’s Dream.

Walter’s “credo about growing old” (she was born in 1950) is voiced by her version of Macbeth’s witches. In 2011 she published Facing It, a collection of photographs of older women, from Jane Birkin and Françoise Hardy to people Walter had spotted on the tube. The book celebrated “a certain ‘alternative’ outlook, an acerbity, a sense of irony”. Her weird sisters challenge those who despise them with a defiant recital of their wrinkles, stubble, creaks and “leopard eyes”. They also rejoice in the “quiet wells” of their memories. “I wish I’d had when young the fuck-it-all confidence I have now,” she says. “The paradox is that you get more confident at the point when the parts have run out…” A spread in Facing It shows her at 18 surrounded by schoolgirls, and with the same women 30 years later: “One of my few qualities is loyalty. I have a lot of best friends.” She has more or less the same bobbed hair and is almost instantly recognisable; the main difference is encouraging: in the second photo she looks more defined, as if she had swum into focus.

The interest in age is itself interesting as for much of her life Walter appeared younger than she was. Her voice was high-pitched enough for her to play Juliet, supposedly 13, on the radio when she was 30. Had she sounded deeper, “I think my career would have been different. I would have been taken more seriously early on.” She was turned down by five drama schools, and when she got into Lamda was told – code alert – that she was “subtle”: she might make it on telly but had too lightweight a voice for the theatre.

Her talk is a particular mixture of candour and detachment: Walter might be a really sharp critic reviewing herself. Unlike Maggie Smith, who claimed never to have seen Downton Abbey, “I do watch myself, and I depress myself. There’s not much you can do about theatre but I learn how to do things differently on telly. It’s very seldom that I’ve looked at something and thought: that was good. About three moments in my entire career.” Pressed for an example, she goes right back to her 1980 television appearance in Ian McEwan’s Enigma-inspired television play, The Imitation Game, and a short sequence when she was calling her best friend, played by Brenda Blethyn, from a phone box; she was stirred by memories of ringing her mother from boarding school.

Asked what she would never wear (the answer is yellow), she flicks her hand dismissively at the ivory triangle of her features: “just look at this pasty face”. Talking about her schooldays – Cranborne Chase – she comes up with a beaming piece of erasure from a school report: “Harriet’s tennis is improving but she still has trouble contacting the ball.” She shrugs off the fact that she turned down a place at Oxford: she sat the entrance exam at the urging of her grandfather, and would have studied languages (Italian, though she has since learned some Russian, which came in useful in Killing Eve). Still, she had decided when she was nine that she wanted to be an actor and didn’t waver, though her grandfather wrote her father a letter saying “Harriet is nuts to want to be an actress and you are nuts to let her”, and her uncle Christopher Lee – he of The Curse of Frankenstein – was conscripted to fill her in on the difficulties of the profession.

The first thing she would say to Shakespeare were he to drop in would be an apology “for the way we have turned out. Four hundred years later and we are even worse. We have not led into the light.” Actually, as far as the theatre is concerned, Walter has done rather a lot of leading. Not least in what has come to be referred to as the “all-female Shakespeares” directed by Phyllida Lloyd, first seen at the Donmar Warehouse in 2012. Walter was the linchpin of the productions: a riven Brutus, a desolating Henry IV, a haunted Prospero. She slipped into the roles without putting the macho into inverted commas: sleek as a needle and utterly authoritative, shorn of the hand gestures that she has identified as one of the ways women express themselves. She was, after all, used to behaving like a fellow. “The people you study when you are a child are either frightening schoolteachers or people you’d like to be like. I thought boys had a much better time so internally I took on their posture and attitude.” Her breakthrough part – tiny but crucial, as it landed her an agent – was as an almost silent young chap in Joint Stock Theatre Company’s 1978 version of The Ragged-Trousered Philanthropists.

The opening of the Donmar Shakespeares was “probably the most frightening moment in my career”. It changed the possibilities for Shakespeare and the theatre at a stroke. Individual women – from Sarah Bernhardt as Hamlet to Fiona Shaw as Richard II – had long taken on leading roles. This, though, suggested that the default position for a cast need not be male, and brought with it – almost unobserved in the excitement about gender – other changes: actors who were not all white; accents from all over the country and beyond its borders; women who were not twig-thin. (Male critics have wondered if men are about to lose the chance of starring roles. Hardly.) Things have certainly come a long way since even 2005, when Walter and Janet McTeer, playing opposite each other in Mary Stuart as Elizabeth I and Mary, Queen of Scots, were asked to hold hands at the curtain call as audiences were worrying that they hated each other.

There must surely be – Walter is thinking about it – a show based on She Speaks! I am also hoping she gets cast in parts that push against her elegant economy: in, for example, a fan-waving, syllable-swilling folderol Restoration comedy. Imagine what she would make of Congreve’s line “I may by degrees dwindle into a wife”. Meanwhile, next year, in a season devised by Ralph Fiennes in Bath, she will appear as the melancholy Jaques in As You Like It: who better to reimagine a monologue about all human creatures that is commonly called the “Seven Ages of Man” speech? Inquisitiveness will propel her. “I grew up being a bit timid but very, very curious,” Walter says. So curious that as a young woman she trailed someone in the street, followed them into the house and got trapped in the cupboard under the stairs. “Some people go backpacking and have adventures. I discovered the world by pretending to be somebody else. You learn an awful lot by travelling in someone else’s skin for a while…”

• She Speaks! What Shakespeare’s Women Might Have Said by Harriet Walter is published by Virago (£20). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply