There is a low-boughed tree in the Chelsea Physic Garden that bears strange blossom: a tall, broad-shouldered woman with a straight spine and a thick bob of dyed blonde hair. It is Dame Diana Rigg, and she is standing under the tree, with her head in the branches, because our photographer has asked her to. When she emerges picking petals from her hair, she looks to the overcast sky and says, 'This flat light is very good for a woman of my age.'
Since she mentions it, she turns 70 this month. And although she looks her age in a way that, say, Julie Christie, her fellow 1960s sex symbol, does not, her strong features - retroussé nose and high cheekbones, down-turned eyes and mouth - are still softly handsome. Dressed in pin-stripe trousers and a red jacket, and with only a suggestion of make-up, she seems comfortable with herself. Too dignified to be vain. Not the cosmetic surgery type. (Actually, that's not quite true. She had the wrinkles around her eyes removed when she was 44, but that was it.)
She lights a cigarette, getting one in before lunch. The last time we met, a decade ago, when she was in Ted Hughes's adaptation of Racine's Phèdre, people were still allowed to smoke in restaurants, and boy did she make the most of that. She still smokes 20 a day, but is relaxed about the smoking ban in public places. We debate whether to eat here at the Physic Garden - she is a member - or round the corner at Foxtrot Oscar. She opts for the latter because they mix a good Bloody Mary there.
As we walk, we talk about Chekhov's The Cherry Orchard. She has just finished a run of it at Chichester - 'Got a right old buffeting from the critics, but I loved it and we played to 74 per cent capacity, so up yours critics' - and is now about to head off for the summer to her place in France, south-east of Bordeaux. There she will cook for friends, read, listen to music and swim naked in her pool. At night she listens to the owls. She feels freer there than in her Kensington flat, more at ease. Because she always despised herself for not speaking fluent French, she took herself off to the Lycée to learn it. 'I'm still chary of speaking French outside France, though.'
At the restaurant she orders her bloody Mary and tells me that the mayor of the French village asked if he could hunt wild boar in the land that goes with her house. 'So they all came in their vans with their dogs and blew their horns and killed two adult wild boar, mother and father. Very medieval. Carried them out of the wood on a stick, but one of the young boars escaped and took refuge under my neighbour's bed. The saying in the village was that she had the pig under her bed, whereas normally he is on top of it.' She laughs at the joke. She is in a good mood, an end-of-term frivolity. Phew. She can be glacial when she wants to be, as a few interviewers have discovered over the years.
When the drink arrives, she asks for another slice of lemon and says, 'I don't normally drink at lunchtime. I'm not saying that defensively, I just don't. And in the evening I never drink before six, an old habit acquired from my father.' She makes up for it after that, though, believing in 'red before bed'. A £3.99 bottle of Chilean merlot gives you the best night's sleep in the world, she reckons. It's like being hit over the head. She wakes up 10 hours later, feeling like a spring lamb.
Though she describes herself as 'hopelessly un-neurotic' and thinks she might be a better actress if she were more neurotic, she does have a sudden and explosive temper, and the angrier she gets the more articulate she becomes. She is intolerant of queue-jumpers, litter-droppers and bad-mannered people generally. When driving, she will roll down her window and yell, 'Thank you!' to people she has let into a line of traffic. I get a taste of this sharpness now, or rather the waitress does, when she appears and says, 'I'm sorry to interrupt, but I'd like to talk you through the specials on the menu.'
'I think we can read,' Rigg says. 'Thank you so much.'
'But they change each day,' the waitress says, staggering back slightly. When the waitress goes, Rigg explains her shortness with people. With her, things have to be said. She's no good at bottling up her feelings. But she is good at saying sorry and she never sulks.
I tell her I found clips of her on YouTube from her various appearances on Parkinson - on one of which she said that her greatest pleasure in life came from biting her baby's bottom - to scenes from The Avengers, the television series as synonymous with the 1960s as are the Mini and the Beatles. I had forgotten how psychedelic those shows were, how surreal the humour - she would end a fight scene by picking up her knitting.
'Oh yes, my daughter sends me YouTube clips. Not of me. Funny stuff. It all sounds like rubbish the stuff they have of me. It's a horrible thought that they are on there. I'm also a mouse pad and a screen-saver. Am I supposed to be flattered? All these old images of me floating across the screen, the terrible chasm of what you were and what you are. I know who I am, but these people who see me as I was then don't. There is always one thing that turns you into an icon, an iconic image, in my case a catsuit. But the icon 40 years later doesn't really want to know because it's not relevant to me. Some of those early photographs of me might as well be sepia. It's always thought that I disclaim television and am too theatre, but the truth is The Avengers bores me now. I was grateful because it catapulted me into stage stardom. It was good. I'm not ashamed of it. But I only did it for two years.'
The leather catsuit was 'a total nightmare'; it took 45 minutes to get it unzipped. Like struggling in and out of a wetsuit. Once she got into the jersey catsuits, they were easy to wear but she had to watch for baggy knees. Nothing worse.
At Rada she had trained as a classical actress and afterwards she had joined the Royal Shakespeare Company. It sounds like she planned to use television as a way of boosting her stage career. 'Not at all. I left the RSC not knowing what I was going to do and ended up getting a telly job with Harry Corbett, only because the director's wife had been cast opposite him and she had to drop out. After that, my agent put me up for The Avengers and I didn't have telly, so I didn't know what it was. When it came out, I was suddenly famous. It was startling. From being anonymous, I was mobbed.'
She certainly was. Once she had to hide in the lavatory at the Motor Show. And in Germany police resorted to batons to hold back the fans. Slavering fan mail was another problem. She would get her mother, Beryl, to field the letters. The replies were usually along the lines of: 'Those aren't very nice thoughts. And besides, my daughter is too old for you. I suggest you take a run around the block.' People still send her Avengers photos to sign, but she refuses. 'I feel such a phony. That is not me. That is another person.
'Fame was different then, she adds. 'Nowadays people court fame, Big Brother-type fame; in those days we didn't know how to court fame. There weren't the channels to court fame, the publicists. I just hope the people getting their 15 minutes now are putting their money in the building society.'
When I ask if fame is hollow, she shakes her head. 'I'm not the best person to ask because, whatever form it has taken for me, it has always been attached to my career. I've always tried to avoid any vestige of it touching my private life. It has always been separate. I step into a character in my public life. People who don't make that distinction are dooooomed.' (This is a trait of hers: she stretches her vowels elastically but not camply; her voice is far too deep and smoky and unhurried for that.) 'There is still that small centre of me that has never been touched by fame, never photographed, written about or discussed. So when I sit next to a stranger at a dinner party and they feel they know something about me, I know they don't.'
In retrospect, she wishes she had allowed herself to enjoy fame more than she did. 'I should have handled it better. Had more fun. Not naughty fun. But just, you know. I sometimes think, when I look back on those days: why didn't I have more confidence? Why didn't I know I was pretty good-looking? It is probably to do with my Yorkshire upbringing. Always thinking that people might be saying, "Who does she think she is?"'
She was born in Doncaster in 1938, but her parents were based in India and she was taken back there after her birth. Her father, Louis Rigg, was a railway engineer who worked for the Maharaja of Bikaner, Ganga Singh. When Rigg was shipped back to gloomy Yorkshire and boarding school in 1945, she felt like a fish out of water. Still, Yorkshire, she believes, played a much greater part in shaping her character than India did. It was a tradition in her household, for example, that you always had to have a slice of bread and butter without jam before you could have one with. Very Yorkshire, that.
Does she keep a diary? 'I don't and I wish I did because the past is pretty unknown to me. I have so lived for the present that I can't remember the details. Smells and sounds can transport me and then I remember. I don't keep memorabilia or photograph albums.'
Her daughter, Rachael Stirling, is also an actress, one with a successful career (she starred in Tipping the Velvet). She looks and sounds like her mother. Was it inevitable that she would follow her into acting? 'Her dad and I did say, "Here we go. Fairly inevitable." But we said she must go to uni first, so she read history of art at Edinburgh.'
Is there any rivalry between mother and daughter? 'No, I don't think so. I feel more that the baton has been handed on. She doesn't use my surname, but she does look very like me.'
Rigg gave up working to raise her daughter; would she recommend that Rachael do the same if she has children? 'The work-life balance, you mean? I wouldn't advise her on anything, she'll do it her way. I might take over the baby if she is away. The world has changed mightily; in my mother's day you were made to feel guilty if you went out. Now everyone is left to work it out for themselves. Actually, acting was quite compatible with motherhood. I could take her to school when doing theatre. The evening was a problem, obviously. But I could always put her to bed when I was doing a film or TV. I don't think my profession made any difference with her, though. My divorce? I'm not sure.'
Her first marriage was in 1973 to Menahem Gueffen, an Israeli painter; her first divorce was three years later. She married again in 1982 to a Scottish landowner, Archie Stirling, and had Rachael at the age of 39. The marriage broke up in 1990, after Stirling had an affair with the actress Joely Richardson. Rigg has stayed on good terms with her former husband. And when we met last time she said, 'I'm slightly aghast that you see before you a twice-divorced woman. I'm shocked. It's not how I saw myself, how I imagined things would work out, not what I believe in.' Now she seems more at ease with the idea. When she was young, she says, women were considered incomplete without a husband, and it has taken her many years to come to the tranquil conclusion that life can be complete without a man after all.
She seems to know herself well, if that doesn't sound like too crass a comment. She understands what makes her tick and is unsentimental and matter-of-fact about herself. She thinks she is probably quite 'anal' - actually, that is what her daughter thinks and she goes along with it. Her greatest fear is being 'a dithering, dribbling old bag, having to rely on help for everything'. Her greatest disappointment is her film career - 'or lack of - but it's too late now.' The single thing that would improve the quality of her life would be to no longer have creaking joints: in the Stephen Sondheim musical Follies, in 1987, there was an 11-minute tap routine in high heels that permanently damaged her knees.
Today, Rigg seems to be regarded by audience and critics alike as the most daring, intelligent and inspired tragedienne on the London (and New York) stage. But it wasn't until she was in her fifties that she hit her stride, playing three award-winning leads in succession: Medea (1992-94); Mother Courage (1995) and Who's Afraid of Virginia Woolf (1996). Rigg's performance as Medea was a career peak. She won a London Evening Standard Theatre Award and Tony Award for Best Actress. In it she played a vengeful wife who kills her estranged husband's children. Coincidental though the timing was, she had just separated from her husband.
In Phèdre, she played the queen who falls in love with her stepson, only to find that her husband still lives. Jealousy induces her to send him to his death, but her conscience forces her to admit her guilt before dying herself. 'With Phèdre it was typical Ted [Hughes] - muscular, strong writing - there is nothing Ancient Greek wafty about it. It grabs you like a pair of eagle's claws. It was a huge privilege working with him. He died during the run of the play. The night he died, we were playing it. Such poignancy - because he knew he was dying and he said to the cast, "I go to bed happy because Phèdre is on stage." He had been so attacked by the feminists who blamed him for Sylvia's suicide. They felt he had driven her to it by his infidelity. He was like an oak and I can quite see why women threw themselves at him. His poetic soul and that wonderful voice that came from his boots.'
Her own soul is pretty poetic. She is, she says, easily moved by the thought of young men fighting and dying for their country. Whenever she visits the battlefields of the First World War she is reduced to tears. 'They are so silent, hardly any birdsong, big open fields, it is as if nature is paying reverence.' At the moment, the news images of Union flag-draped coffins coming out of RAF transporter planes fills her with terrible despair and anger. She joined the march against the war in Iraq and says that she now feels betrayed by Blair. 'Did he seduce me? Yes. He, generally speaking, courted my profession. But I now disavow.'
Her father was a Conservative. So is her brother, a retired RAF Harrier test pilot. She is a crossbencher. 'I wish I could feel sorry for Gordon Brown, but I can't. He was the understudy who got the role but didn't understand it. Didn't know what to do with it. He didn't learn his lines or know his moves. I heard an alternative comedian say that even when Gordon smiles he looks like he's sh--ting a sea anemone, and that's about right. The breathing? It's a tic. A habit. He inhales and his bottom lip goes with it. He could easily see an acting coach and get rid of it, but I imagine he is too busy with other things.'
She is a big Barack Obama fan and thinks John McCain is too old for the job. 'I know I should be saying the opposite because I'm the same age as him, but I do think his age will make a difference. At 70, you aren't as physically robust as you were. I don't think your mental capacities are as good as they were. The President should be a younger man with older advisers.' I remind her that the last time we met she had been telling me that she intended to get a pensioner's bus pass. Did she? Actually, she says with a quick smile, she drives.
I have to say I do not recognise the woman who, in 2002, was attacked by the Daily Mail as 'embittered'. She had gone into retirement, the paper claimed, and was living 'the life of a recluse' in France. The article was accompanied by a grim photograph of her clutching a baguette. The caption read: 'Shopping for one.' She had been followed to her remote village and secretly photographed. She sued the newspaper for libel and won £38,000 damages, which she donated to charity.
That said, she does quite enjoy silence and her own company. She is still a keen fly-fisher, a solitary sport. 'I don't have a river any more. I did have when I was married, on my husband's estate. Now I just fish whenever I am invited anywhere. I'm a fishing tart.' She is still the chancellor of Sterling university, though she stands down this year. 'I'm not an academic, but I would have loved to have been one. I love the dinners with professors. You learn all sorts of things. I can tell you all about the mites that attack salmon. I can even tell you what happens in the lochs with the mounds of fish excrement.'
The life of an actor has never been secure, she says, because actors never really know from one year to the next what they will be doing. 'But the grave danger is to fall into the trap of thinking you cease to exist if you no longer have a job. Obviously, economics has a bearing on this. But you must fill your life with as many alternatives as possible to your job, because without that you are going to be an empty vessel.' So what does she have lined up next? 'Nothing next.' She says with a laugh. 'But I still exist.'
Afterwards, as I am waiting for a taxi in Chelsea, I hear a woman calling my name. It is Rigg in the driving seat of a new-looking, sky-blue Mercedes sports car. Can she give me a lift anywhere? So much for the bus pass, I think. Just then a taxi arrives and she gives an ironic salute goodbye. It is a very Emma Peel moment. I think she was even wearing sunglasses and may have had a cigarette in her hand. Either way, she looked like the coolest damned 70-year-old I've ever seen.