"Darling Carol,

Here is the second part of your Christmas present. Alas we still haven't been able to get nice earrings for pierced ears. I don't know what kind of Christmas it will be for us. You remember that last year 'Afghanistan' happened on Boxing Day. This year we will keep a watchful eye on Poland, but at home we have the hunger strike in the Maze Prison, and it looks as if those on it are going to continue until death – and that would be about Christmas time. Our fear is that those deaths would cause violence and strife on the streets in Northern Ireland.

The next six months will be difficult politically, especially with rising unemployment, but we shall have to ride the storm. Economically things will get better before the unemployment figures fall.

Much love – will phone you over Xmas

Mummy xx'"

Few children have letters like this among their treasures, but to Carol Thatcher it was fairly ordinary fare. The mum who switched between domestic detail and international affairs in the space of a paragraph was just "mummy" to her, not the scary stateswoman who so often made grown men tremble.

Margaret Thatcher, the grocer's daughter from Grantham who'd studied chemistry at Oxford before turning to law and later honing her razor-sharp mind in political debate, was simply a working mother to her twin children Carol and Mark, although Carol considers her mother and father Denis "a couple ahead of their time" in that no other family she knew had two working parents.

Margaret became an MP (one of only 12 female members of the House back in 1959) when the twins were six. Carol can remember crowing about it to her friends, and even quizzing a friend's mother once about what she did all day while her own mum was out being an important person.

Life was lived at a frantic pace, with the Thatcher household's life punctuated by words like "division bell", "three-line whip", and "constituency". MPs' holidays were long, so while the children saw less of Margaret and Denis during their boarding school terms, holidays to the Isle of Wight were adhered to, even if Margaret usually had a pile of constituency paperwork with her. Carol Thatcher recalls the day in 1975 when her mum became leader of the Tory Party; it was the same day that she, Carol, had a finals exam for her own law degree from London University. On seeing her jittery daughter sitting at the breakfast table, Mrs T chided: "Well, you can't be as nervous as me."

Later, when the exam was over, the invigilator came over to Carol and asked if she knew the result of the final ballot. She didn't but he told her. "A shiver went down my spine," she remembers. "It was hard to believe that this could happen to a family like ours." She walked home to Chelsea through the rain, and knew it must be true because the kitchen floor was covered in buckets of blue-beribboned congratulatory bouquets.

While her mother collected the keys to Number 10 a few years later and ran the country for more than 11 years, Mark Thatcher busied himself becoming The Embarrassing Family Member. Denis Thatcher continued with his various business dealings, as well as enjoying golf and gin in equal measures, and Carol spent four years in Australia.

Although she denies that she put so many thousands of miles between herself and her family in order to escape the constant association and comparisons with her indomitable mother, it does look that way.

"I'm a complete travel nut, and it (Australia) is the love of my life... You are always going to be compared, yes. Did it worry me that I didn't measure up? I didn't ever think it was a competition. We inhabited such different worlds."

Carol describes in her memoir, A Swim-On Part in the Goldfish Bowl, how on her return to London she became "first reserve" whenever a guest at a Downing Street or Chequers "do" cried off. She would get the call to "brush up" and make up the numbers with head of state and their spouses and other members of the international political glitterati. But a strict rule was always attached to these last-minute invitations. "My mother made it very clear: 'If you walk out of lunch at Chequers and tell your journalist friends what you've heard in conversation here about government issues you'll never come again'." Carol kept schtum.

Life in the Thatcher family certainly did not turn her into a political animal. She says she had to tone down her own opinions in company ("I always had to think about what things I said would look like in print...") and at university had got used to the fact that colleagues regularly went off to demonstrate against her mother's agenda as Education Secretary, which involved unpopular changes in student grants and the school milk policy that led to the soubriquet "Thatcher, Thatcher, milk snatcher".

The memoir is a strange read. Jolly and bluff in its tone – much like Carol Thatcher herself – it gives fascinating insights into the strain on the family of living through the Falklands crisis of 1982 and the terrible time when Margaret Thatcher was "booted out of Number 10" as her daughter puts it. But it gives little away in terms of the minutiae of Carol's own life, and very little to do with emotion.

Margaret Thatcher's Iron Lady carapace and ability to contain any feelings well within herself were two of the hallmarks of her premiership – and this made the famous photograph of her weeping in the limousine that bore her away from Downing Street for the last time so shocking.

Were Margaret and Denis, who met on a blind date, by the way – a loving, happy couple? "Well, they were of that generation..." What does that mean? "Their generation viewed marriage and relationships differently. Love and loyalty were taken for granted, part of the package. I hugely admired them for that."

Carol doesn't think she has inherited many characteristics from her mother – although she does a good line in trying to answer some question other than the one asked, and has a faintly familiar booming voice – but says she has inherited her late father's mischievous sense of humour. She clearly adored her dad. "I think my father turned in an Oscar-winning performance in a part he never auditioned for. He never thought he'd be the husband of Britain's first female PM. He was shy. He didn't want to go to the Tory Party Conference and gland-hand the faithful. He said: 'I was shy, but I had to un-shy myself pretty quick, in order to be better at it'."

The most fascinating and poignant section of the book is the description of the kind of decompression sickness that struck Mrs Thatcher when, after she was ousted in 1990, she suddenly found herself a homeless backbench MP. That day was the only time Carol ever saw her father cry. The fall-out for Carol, apart from doing all she could to support her mother through the dark days following her fall from power, was that she found out who her real friends were. "Half the people I knew didn't ever talk to me again. Did I mind? Did I hell!"

It's explicit in the book that Carol Thatcher feels she only really came out from her mother's huge shadow when she won her Queen of the Jungle crown at the end of the 2005 reality TV series I'm A Celebrity, Get Me Out of Here!

It's difficult to imagine Carol explaining to her mother that she was going to live in the Queensland jungle for three weeks while cameras watched her every move, and viewers voted for her to stay or leave the show. In the event 11 million viewers saw her taking a pee al fresco, vomiting after a sky-dive and eating grubs and a kangaroo's testicle. The experience seems to have been the high point of her life so far, and a political upbringing proved useful in the jungle. All that gung-ho, must-get-on-with-it, don't-whinge and never-say-die went down a storm with fans of the series.

After her victory, Baroness Thatcher put out a statement saying she thought her daughter had won "in typically Thatcher manner". The programme proved a great launch-pad for a much more varied media career for Carol, who's now 55.

There's been criticism from various quarters of Carol's decision to describe her mother's dementia in detail in the book. It isn't news – statements about her health, including a series of mini-strokes and the dementia have been made over recent years.

Yes, seen from the daughter's perspective, it must have been utterly shocking to find that your mother, whose brain and powers of analysis have always been famously without peer, is suddenly confusing Bosnia with the Falklands and asking the same question three times in three minutes.

"I'm mystified (by the flak). It's generally a very 'up' book, but I couldn't make it (my mother's illness) sound like a fairytale. If you put it in you get flak, and if you leave it out, you get flak. I talked to a friend in a similar situation, and I thought I wrote about it with some sensitivity."

The problem, for this reader at least, is not that the dementia is mentioned; after all, which family in the land has not been affected by the disease? But Carol does rather over-egg the unnecessary detail, sharing anecdotes about her mum forgetting newspaper headlines she had just read and later even forgetting, over and over, that Denis had died.

It seems so... heartless. But Carol's crisp justification is that she is her mother's daughter, and Maggie taught her to "say it like it is". We have no way of knowing what Margaret Thatcher might think of that.


A Swim-On Part in the Goldfish Bowl by Carol Thatcher is published by Headline, £18.99. To order a copy from the Yorkshire Post Bookshop, call free on 0800 0153232 or go online at www.yorkshirepostbookshop.co.uk. Postage and packing is £2.75.