By Michael Cockerell
Political documentary maker
Mark Thatcher (r) remembers his mother being very busy
As Hillary Clinton licks her wounds over the failure of her $100m campaign to win the Democratic nomination, she might be interested in getting a copy of - or downloading on BBC's iPlayer - my TV documentary The Making of the Iron Lady.
It tells how Margaret Thatcher overcame all the odds to become the first female leader in the western world nearly 30 years ago.
For the documentary I wanted to speak to those who had been closest to her - as sadly Lady T no longer gives TV interviews, on doctors' orders.
I knew that her son Sir Mark Thatcher, who inherited his late father's title, had never agreed to talk about his mother before and that his relations with the media have been characterised by mutual antipathy.
I worked hard to assure him that I wanted his first-hand account of how his mother became prime minister. To my agreeable surprise he agreed to the interview.
Sir Mark recalls how mother's motto was "never a wasted moment".
"I remember how she used to come home from Westminster and immediately start cooking the dinner. And I would go up to her and say 'You know mum it's OK - you can take your coat off now'."
'Out of the ordinary'
We discovered film of Mrs Thatcher giving her own first TV interview in 1960, with her then six-year old twins, Mark and Carol, perched on the sofa watching.
"I remember when the TV crew came down for that interview," says Sir Mark.
"It was the first time I realised that my mum was not like my schoolfriends' mothers: she was clearly something out of the ordinary'."
She rose fast through the Tory ranks and in 1970 became what the new Tory prime minister, the bachelor Ted Heath, called "the statutory woman" in his cabinet.
But four years later - after Heath had lost two general elections in six months - the Tory knives were out for him.
Mrs Thatcher decided that if no other member of his cabinet would challenge Heath for the leadership, she had no alternative.
"Mum felt that the party had moved too far to the centre," says Sir Mark. "She certainly didn't stand to advance women's causes.
"Her decision to stand as a candidate for the leadership was one which was taken over a short, but nevertheless considered period of time.
"My father's concern was that if she stood she would poll very badly amongst the Conservative members. And that would damage her political reputation for ever."
All the polls and pundits saw Mrs Thatcher as the outsider who was bound to lose the leadership election.
She chose her oldest political friend, the right-wing Tory MP Airey Neave, to run her campaign.
Airey Neave compared Tory MPs under Ted Heath to prisoners in Colditz
An Old Etonian and MI6 agent, like James Bond, Neave had been the first Englishman to escape from the Nazis' notorious prisoner-of-war camp Colditz Castle.
Thirty years later Neave deployed his spooky skills in Mrs Thatcher's cause.
Her son says: "Airey compared Conservative MPs under Ted Heath to the prisoners in Colditz Castle - and they needed to be persuaded to his way of thinking as to how to escape."
Neave's undercover campaign worked. Mrs Thatcher toppled Ted Heath.
My documentary tells the story of how she did it. I ask Sir Mark why he felt his mother had broken through the glass ceiling to become Britain's first female prime minister.
He replied: "My perspective as her son is very straightforward - she was the best man for the job."
Michael Cockerell's The Making of the Iron Lady will be repeated on BBC4 at 2255 BST on 12 June.