Born: 23 September 1954 in Bury, Lancashire
Family: Parents - Tony Booth and Gale, both actors; sister, Lyndsey, (43), a practitioner of holistic medicine; half-sisters - Jenia (37), Bronwen (36), Lauren (30), Emma(28), and Joanna (nine)
Famous stepmother: Pat Phoenix, Coronation Street's Elsie Tanner
Marriage: To Anthony Charles Lynton Blair on 28 March 1980 at St John's College Chapel, Oxford
Children: Euan (15); Nicky (13); Kathryn (11)
Education: St Edmund's Roman Catholic Primary School, Liverpool; Seafield Grammar School, Crosby; London School of Economics (LLB).
Legal career: Called to the bar in 1976; Queen's Counsel 1995; Assistant recorder, 1997; legal personality of the year, 1997
Political Career: Labour parliamentary candidate for Thanet North in the 1983 general election. Executive member, Labour Co- ordinating Committee 1983-85
Hairdresser: Andre Suard of Michaeljohn, Mayfair, London
Hobbies: The theatre; keeping fit; "enjoying my children"
She says: "I started life as the daughter of someone, now I am the wife of someone and I'll probably end up as the mother of someone." "Once you succumb to Tony's charms you never really get over it. If you met his father, you'd see where he gets it from".
He says: "Cherie is the rock on which my life is built. I'm lucky. I'm in love with Cherie. I still feel like that about her. She keeps me anchored. Cherie is very tough with me sometimes. If I get down, she's there saying: `Look, you've got to expect these things. Now for heaven's sake, pick yourself up, dust yourself off and start all over again'. You lose a lot if you don't have emotions churning about within you"
It will, of course, be the most political pregnancy and birth since - well, since Gabriel whispered the good news to the Virgin Mary. Forget, "Vote New Labour". At the next general election, "Vote New Baby" will probably suffice. Unless Ffion Hague can come up with a multiple birth, the Tories are permanently snookered.
But this particular propaganda coup will not be without its potentially serious bouts of infant croup. For, while the nation rightfully rejoices (or at least feels a passing warm glow) what lies ahead for Cherie Booth is a totally new double challenge - and perhaps her toughest yet.
The first issue to be faced is the physical demand of pregnancy at 45; a doddle one might guess if her present levels of energy are any guide. The second and far trickier feat will be in forging a fresh role for herself as the mother of a new baby who also has a career to which she is committed - a QC with ambitions to become a judge. For the past two years, after the nightie on the doorstep incident (when she was photographed opening the front door first thing in the morning and in a rather dishevelled state), she has risen as a phoenix from the flannelette ashes, to turn herself into the silent clothes horse at her husband's side.
This Fifties fixation with acting as your spouse's adornment is something that I, amongst others, initially found highly irritating - not least because Cherie is a barrister and a mother of three with, presumably, better things to do. Then it was pointed out to me by someone rather close to her, that this was the lesser of two evils. Appearing as a walking wardrobe (lots of photo opportunities) was wiser than opening her mouth in interviews and finding herself accused of pillow talk or, worse, holding opinions rather to the left of the PM (Old Labour's nightmare, torture by tabloids). Besides, according to one friend, it isn't so much that she needs him - as he needs her in his far-flung corner of the world.
Pregnancy and motherhood in the late Nineties, however, requires a completely different set of tools. Over the next year or so and beyond, Cherie will have to move from wardrobe to wet wipes. She will no longer be judged by what she wears or how adoringly she gazes on Tony - what will matter most is how she (and her husband) behave as parents of a newborn.
A sensitivity to this has already been revealed by the announcement that Baby Blair will be delivered in an NHS hospital. To quote the feminist slogan, "The personal is political", but never more than when it burps, comes in nappies and is labelled the Prime Minister's child.
"When the Blairs had their first three children, we lived in different times, the family was invisible in the workplace and it was up to the mother to cope as best she could ," says one Labour MP.
"Now, more women are in employment, and more dads want involvement with their kids. My constituents tell me they'd like more recognition of the dilemmas they face - and more government action. Family-friendly policies are part of New Labour's rhetoric - but it doesn't add up to much much in practice yet.
"How Cherie plays career and late motherhood will be very carefully scrutinised - and judged. She could really make a difference - but will she dare?"
So, will Cherie go back to work within days as she did with her earlier children, Euan, Nicholas and Kathryn, (attracting the wrath of the mothers- at-home in Middle England)? Or will she demand full maternity leave, raising the issue of how inadequate these "rights" continue to be in Britain. (Although, this week, Gordon Brown promised improvement).
Will Tony, a great advocate of the responsibilities and duties of fathers, opt for parental leave? If he does, since it is unpaid in the UK, the pundits will no doubt praise him as a nouveau pere and damn him for exercising a privilege that the majority of the lower-paid electorate can ill afford. And how will the Blairs manage for childcare? A nanny will be too Islington, a childminder much more warmly welcomed - but on the minimum wage? Hardly upping the value of caring and giving - as Blair once promised - dignity to labour.
In short, more by cock-up than design, will Baby Blair become a wonderful millennial catalyst for the desperately stalled issue of the needs of all our children in this workaholic world? Might the normally politically cautious Cherie prove the mother for the job, creating a real cultural shift in our attitudes to the work-life balance? Or could it all end in tears?
Cherie Booth is, of course, smart - and driven. Born in Bury, Lancashire, she was brought up in Waterloo on Merseyside, north of tough Bootle but not as posh as Crosby. She was, according to John Rentoul in his biography of Tony Blair, one of the cleverest girls at her convent school, Seafield Grammar. She gained four A grades in her A-levels.
A major influence, according to one friend, is Cherie's mother Gale. Cherie's father, the colourful actor Tony Booth, left when Cherie was under five, and Gale raised her and her younger sister, Lyndsey, as a single parent with the help of Tony Booth's family. It was a matriarchal household headed by Granny Booth (Tony Booth's grandmother).
We now all know now that Cherie got a First in Law and came top in the year's Bar exams (while Tony Blair received a Third). She joined the Labour Party at the age of 16 in 1970 and was fighting her own election at Thanet North in Kent, in the general election of 1983, when her husband won Sedgefield. In her campaign she invited the veteran left winger Tony Benn and her father, also on the left, to address a public meeting at Margate Town Hall. Tony Blair was in the audience.
The pair first met when they were sitting together by alphabetical accident when they were waiting for an interview for a scholarship at the Inns of Court in 1976.
Cherie's romance with Blair began in the barristers' chambers of Derry Irvine, where they were both trainees working for the man who was later to become Blair's Lord Chancellor. At a friend's party at Christmas 1976 they played a silly team game which involved physical contact, passing a balloon held between their knees. It was then, according to friends, that Cherie realised that Tony could be something more than a colleague. "The next day we went out and to lunch and hours later we were still there," said Tony. "I found her immensely physically attractive and I wanted her as a friend as well."
She is cleverer than he is; he is politically far more astute. "Cherie is completely driven but she knows the dangers of spreading herself too thin," says one friend. "She has chosen to rise in law and leave the politics to Tony - but that doesn't mean she no longer has causes."
Just before John Smith's death in May 1994, the rarely quoted Cherie said: "The fact that Tony's fairly famous and I'm not doesn't bother me at all. I'm very well paid and highly regarded in my own field." In work, contrary to press reports, Cherie no longer earns a quarter of a million a year - half that is more likely, largely because of the demands on her time of being the Prime Minister's spouse. But clients queue not just for the name and a small slice of history ("I was represented by the PM's wife") but because she is excellent at her job, dealing mainly in employment law, European law and the fast-expanding and lucrative field of judicial review.
A clue as to how she may react in coming months is that her passion is children. She has become patron of half a dozen charities, most of them touching on the lives of the young - among them cancer and domestic violence. She works hard for Justice for Children, an NSPCC campaign to make the criminal justice system fairer. "She came to a meeting and spoke brilliantly from the heart without notes," says one colleague. "At times like that, you realise just how hard she must have struggled as a highly capable opinionated professional to shoe-horn herself into the occasional role of the little woman."
Cherie Booth is, above all, a person of paradox. She is a devout Roman Catholic in a secular world and a high-flying feminist who appears happy to perform traditional wifely duties. "Most women of her and my generation, who have been witnesses to divorce and family break-ups, are wary of total emotional investment. We hold something back in a relationship," says another long term friend. "She gives her all to Tony and he feels just as strongly. She is extremely wary of the media, so she often comes across as cold and aloof. But in private she is funny, acidic, a truly caring person - but nobody's fool."
Two years ago, Cherie Blair behaved like an amateur actress who had strayed on top the wrong set. Her wariness gave her face a rictus instead of a smile and the clothes were nearly always two sizes too big. But as her personal strategy has worked well, so her confidence has grown. Tony Blair has described Cherie as his rock. The marriage has become the one soap opera we can watch in the comfort of knowing that this relationship may actually end in "happy ever after". We know too that on the Blairs' 18th wedding anniversary (they married in 1980, in Blair's old college chapel in Oxford), they had dinner together at Chequers while, "My Cherie Amour" was played. Aah.
That "aah factor" will grow stronger once a bump begins to show and Cherie's maternity clothes become the new national obsession. So far, Cherie and her aides have skilfully forged a path which has kept her out of trouble but still in credit with most of the electorate. At the same time, she has brought the names of many estimable dress designers - Ronit Zilkha, Paddy Campbell - to the country's attention.
What would be truly impressive would be if she now guided the nation's eye to the value of caring and the issues that effect every family struggling with home and work, simply by the choices she makes. Many congratulations, Mrs Blair - and please don't keep mum.