Britain's first lady on Mrs Yeltsin, Mrs Clinton and Mrs Blair. Photograph by Alistair Thain
"You're welcome to try," said the Prime Minister dubiously, "but she tends to stiffen up when she's asked questions like that."

Weird stuff. One minute you're standing in a visitor's room at 10 Down0ing Street, watching the rain and looking at a vast ornamental sword in a box, a gift from Wilkinson Sword commemorating "50 Years of Peace". The next minute, a voice behind you - clearly the butler or a footman, only more friendly - says, "Sorry to keep you waiting. I'm afraid she'll be a few minutes longer." And blow me down if it's not the PM bearing down on you, in powder-blue shirtsleeves and big smile. Instantly, all sense and coherence are wiped from your mental Resources Department.

Mr Major, you say, idiotically, I, er, didn't expect to see you here.

"But I live here," he counters astutely. "And you've come to interview Norma."

Thanks for the reminder. Mr Major's face is so extraordinarily familiar that for a second you feel you're talking to a television screen, like a mad person. Just back from the family's hols in the south of France, he is tremendously relaxed, even skittish. He chats about the press and the morning's news, makes to leave at least three times but keeps returning, as though yanked back by your electromagnetic charm. What a nice man. As everyone who has met him says, you'd vote for him like a shot were a ballot box magically to materialise in the downstairs loo.

"And you're going to talk to Norma about Chequers?"

Ah, yes, you say, seized by a sudden desire to tell him everything, but that's only, ha-ha-ha, a cunning smokescreen behind which I'm trying to establish her views on crime, health and Europe.

"You're welcome to try," said the PM, "but..."

But this is where we came in.

Mrs Major is standing in the upstairs drawing room. The furniture is elegantly anonymous, the sofa and carpets indistinguishable from what you'd find in an afternoon stroll round any National Trust mansion. Norma, at first sight, is a picture from a Dictionary of Abstract Nouns, one illustrating the word "Diffidence". She wears the smile of someone who, while trapped in a quicksand, has just been informed that their library book is overdue. Call me a dreamer, but I could swear this woman does not want to meet the press.

Her handshake is firm, however, as she tut-tuts about the rain and explains how, since the Whitehall bomb, they've had armoured windows installed which can only be opened by vintage-car crank handles. Not for the first time, you register the fact that being a First Lady means doing a lot of explaining and pointing out, a lot of facts and info.

She talks animatedly about her new book, Chequers (published next week by HarperCollins), a coffee-table history of the prime ministerial retreat in the Chiltern Hills, with lots of anecdotes about the various incumbents, from Lloyd George onwards, who have weekended there since Lord Lee, a philanthropically minded MP, presented his family seat to the nation in 1921.

Was there one PM she'd particularly liked writing about? "I liked the idea of Attlee - an austere man - giving a children's party; there's a very sweet picture of him standing on the doorstep, handing out goodie bags as they went home. And I was very interested in Ramsay MacDonald. I felt rather sorry for him because he was so shabbily treated. People were always saying, `Oh, he's off down the country and forgetting what he should be doing'. They thought he should be stuck here [Downing Street] all the time. I feel very defensive about that. I know that the work doesn't stop wherever you are. Even now, some people aren't happy to think the Prime Minister could have two days off at the weekend." She bridles. "Chance would be a fine thing."

It's piquant to find, in Lord Lee's trust deed, the words, "It is not possible to foresee from what classes of conditions of life the future wielders of power in this country will be drawn." His lordship certainly couldn't have predicted the arrival on his family's doorstep of the "classless" Mr Major, nor that it would be his wife who would so handsomely memorialise his home, from the red brick chimneys and mullioned windows to the Norma Major rose - a gorgeous pink creation launched by a Nottinghamshire grower at the Chelsea Flower Show - that flourishes by the garden's south wall. But you feel the peer and the chronicler would have got on.

As many heads of state and their wives will have discovered, Mrs M grows on you. She's very poised and rather regal, where you were expecting awkwardness, and unexpectedly chatty and charming, where you thought you'd meet reluctance. Her face is softer and prettier than photographs allow, with a becoming Cote d'Azur tan, and she fixes you, once she's relaxed a bit, with a frank, inquiring gaze. She's too cool to be called motherly, and too straight- laced to be an ideal tango partner, but you'd trust her completely as a confidante and problem-solver.

How had she got on with the other first ladies? Did she have a favourite? "I like Mrs Yeltsin a lot, but that may be because I've seen her more than the others. She's very warm and easy to talk to." Had she seen Liddy Dole at the San Diego convention, explaining to the delegates about "the man Ah lurve". Now that Norma herself is going on the election hustings, did she see herself doing that? "No, I couldn't do that!" She practically squeaks with horror. "I wouldn't do that, no matter what the pressure. I think it's so tacky."

I think of Hillary Clinton and her doomed health crusade, and say: Wouldn't you like to take a more public role? "No, I think I wouldn't," said Mrs Major decisively. "We try and solve problems that come through the post - we have sometimes made a difference on the quiet - but I'm not a Member of Parliament. All I can do is pass it on to someone who might be able to do something, and the fact it's come from me, maybe that'll put it at the top of the heap."

My campaign to extract a clear policy statement from Mrs M is floundering. I can't believe, I say, that someone born in Housman country and raised by the English seaside would be in favour of a single European currency. Does she ever have a word in her husband's ear about it? Her eyes get defensive. "Well, of course I could. But I don't think I need to tell him." And did she have a view about it? A long silence, and she says firmly: "I think I share my husband's view."

Blast. The PM was right.

She was born Norma Christina Elizabeth Johnson in Wenlock Edge, Shropshire. Her father, Norman, an army officer, died in a car crash a week after the war ended. Norma was three. A year later, she was sent away to boarding school at Bexhill-on-Sea. Did she remember arriving there, aged four? Typically, Mrs Major puts a positive construction on it: "It was a lovely house - I've been back to see it, and it's a lot smaller than I remember it, of course. It's a nursing home now." But didn't she feel abandoned? "Well - there was a big toybox in the playroom, where we were required to put our toys when we got there. I had a doll, a big china doll that had to go in this toybox, and it got broken" - she stops, as though struck by the enormity of the memory - "No that can't be right. I can't believe anyone would expect you to put your china doll in awith all the other junk..."

If I were Anthony Clare, I would say that an encounter with Grown-up Land, 50 years ago, has left Mrs Major with a nasty psychic bruise and a certain emotional chilliness. But she rejects this. "It was a very friendly school. And Mum would come down every weekend on visits and stay in Mrs Salter's guest house. We used to go on the pier at Hastings and eat buttered toast and listen to the Palm Court Orchestra and go shrimping. Really, I have happy memories of all my schooldays from four to 18."

Her CV is brief. She taught needlework and domestic science at Battersea College of Domestic Education, worked as a nanny for June Bromfield, the singer. She met John Major, then working in a bank, at the GLC election campaign in 1970 - it was, by all accounts, love at first sight - and married him the same year. Apart from bringing up Elizabeth (now 24) and James (21), and doing constituency work in Huntingdon, she has remained stolidly unimpressed by life outside the family hearth. Indeed, she seemed to dread it, confessing to feeling "physically sick with terror" when her meteoric husband was handed the Foreign Office in 1989.

It's this timidity that may account for her unfortunate treatment by the press. From the day after election day (when, oh consternation, she appeared in the same blue frock twice running), to the recent announcement of the pre-election charm offensive, the press has been on her case, calling her "dowdy" and "ordinary", outing her as a Teasmade abuser, satirising her as a fanatical cooker of peas. But she seems to have conquered her fear of Fleet Street's Finest and can laugh off their more fanciful strokes. She asked me to explain to her the black arts of the "cuttings file" and I pulled out a two-inch-thick pile, through which she leafed, agog. "Good Lord. How extraord... Good Lord, listen - `The book tells of Norma's friendless world' (she laughs delightedly). And what's this? `All of a sudden she was expected to sleep in the cramped, inhospitable private quarters of Number 10.' But that's not true. They're not inhospitable. They're not cramped."

What has exercised her most recently, it seems, is the way the tabloids got at her son, James, over his relationship with Elaine Jordache, a woman 12 years older than him. "It isn't a scandal," says Mrs Major. "She's been divorced for a year, but the newspapers don't want to accept that. They're still writing about `James's married girlfriend' because it makes a better story. I resent that. I don't think it's anybody's business."

Apart from that (Mrs Lincoln), did she enjoy being a prime minister's wife? All those free seats at the opera... "I only asked for a free ticket once" she says firmly, "to see Don Carlos, which I love." She giggles. "Jeremy [Isaacs] was so sweet. He said, `How many?' I said, Just one, Jeremy, I'm being quite selfish about this." Did couturiers thrust their creations at her? She looked blank. "I don't use them. I can't afford them. And, no, they don't offer." What about the lovely dove-coloured silk suit she was wearing? She looked down in an incurious, what-this- old-thing way. "Yes it's nice, but I got it off the peg from Windsmoor."

What did she most enjoy about power? "I think the thing I'll miss most is sitting in the front row. It's great - wherever you go, you sit in the front row. It'll be quite a shock, seeing the backs of people's heads again."

How on earth will she give it all up? She regards me steadily. "We have a home of our own." You know what I mean (I say), have you got life planned out for when you leave here and Chequers and all the rest of it? "Oh," she said with sudden blitheness, "we'll cross that bridge when we come to it. We're not planning for it just yet." Would it be a blessed relief to go? "Let's put it this way - I'm not in a hurry to leave. But it won't be a problem when the time comes."

Last question: did she have any advice for Cherie Blair? Mrs Major emits a charming peal of laughter. "Oh, I wouldn't presume." Her sweet, suddenly animated face is all kindly benignity. "I think we all have to make of this job what we can. But I've no brief. She'll do it her way."

I've checked the tape. I've listened again and again. The Chequers chatelaine definitely doesn't say "She'd". She says, "She'll..."