Pamela Digby was just 19 years old when she agreed to marry UK prime minister Winston Churchill's only son, Randolph, on the day they first met.
The union, short as it was, changed the course of her whole life.
While their rush down the aisle was hastened by young Randolph's desire for an heir, it was Churchill's family who grew fond of the red-haired aristocrat during the anxious, long evenings of World War II.
In fact, Pamela was so trusted by her father-in-law that she became his confidante and helped gather intelligence for him.
Isolated and ravaged by conflict, Churchill's Britain needed reliable allies and valuable information in the battle against Nazi Germany. Pamela appeared to be the solution.
She seduced important Americans, such as Roosevelt emissary Averell Harriman, picking up pieces of intel to bring back to the prime minister.
The details of these information exchanges are unknown, but it is author Sonia Purnell's belief that Pamela played a pivotal role in the early war-time alliance between the United States and the United Kingdom.
"She was [Churchill's] secret weapon, she was incredibly helpful," the writer of Kingmaker: Pamela Harriman's Astonishing Life of Power, Seduction tells ABC Radio National.
"She would often go late at night, sometimes through a raid in an armoured car, to Downing Street to tell him what she had learned and what the Americans were thinking."
Pamela's early life saw her branded the "the courtesan of the century" and eventually paved the way for a second and third act, as a Democratic powerbroker in the United States and, in her final years, as an ambassador to France.
It was in this last role, her first in public office, that she died at the age of 76, after suffering a brain haemorrhage while on her usual swim at the Ritz Hotel in Paris.
Admired by presidents, diplomats and businessmen for her judgement, humour, charm and friendship, her critics branded her a gold digger; a thrice-married seductress with a history of scandalous entanglements with powerful and wealthy men.
Decades later, opinion still seems to be split on the lasting impact of Pamela Harriman. As one reporter put it, her path to power "isn't one you'd recommend to an ambitious woman today, either for her own sake or, not to sound too stuffy about it, for democracy's".
But in her book, Purnell seeks to salvage Pamela's reputation and ponders the question of whether her social life overshadowed her true legacy.
When Pamela became a Churchill
Pamela Digby was born into the old aristocracy and was expected to take part in the traditions that defined Britain's upper class.
The daughter of the eleventh Baron Edward Digby, and the Honourable Constance Bruce, she was raised in a 50-room stone mansion in Dorset with all the trappings of wealth, but very little actual money.
The expectation was that Pamela would "marry a rich nobleman", according to Purnell.
But her first foray into the British court was a flop. Pamela's debut season delivered a few lifelong friends, but no serious offers of marriage.
Her failure to become a "diamond of the season" may have partly come down to her choice of conversation topics, which were more suited to the halls of Westminster than the parlours and ballrooms of high society.
"She wanted to talk about Hitler and what was happening in Europe and Czechoslovakia, and this was considered to be totally unladylike and inappropriate," Purnell says.
"So her life was really going nowhere."
And then the misunderstood Pamela met Randolph Churchill.
After a misspent youth of hurled insults, lost card games and parental censure, the Churchill heir was preparing to go to war and hoped to sire a son before he died on a battlefield.
Spoiled and arrogant, he suffered several failed proposals before a friend set him up with Pamela. He rang her up, invited her out to dinner and made her an offer of marriage that same night.
Pamela accepted, lured in by the promise of a life away from rural Dorset and an entry into the thrilling world of politics.
She married Randolph in October 1939, a month after World War II began, and had a son a year later.
"I was born in a world where a woman was totally controlled by men. I mean, you got married and there was kind of no alternative," she said.
Under the shadow of war, Pamela became close with her parents-in-law, Winston and Clementine.
Their home was a hub of activity in WWII, with generals, admirals, air marshals, advisors and ministers coming and going at all hours of the day.
It was here that Clementine first observed Pamela's power over older men "through a rare cocktail of flattering attention, smouldering sex appeal and an impressive grasp of geopolitics", according to Purnell.
From these exchanges, a scheme was conjured. It was thought Pamela could help win the Americans over to the British side.
With the help of one of Churchill's chief advisors, Lord Max Beaverbrook, Purnell writes that Pamela was "unleashed as the Churchills' most willing and committed secret weapon".
Winning over the Americans
Randolph Churchill was too preoccupied with drinking and gambling to see what was planned for Pamela.
Their marriage had been less about love, and more of a business transaction. And for most of WWII, the younger Churchill was away in the Middle East on military service.
Alone, Pamela decided to move to a cheaper apartment in London and got a job with the Ministry of Supply.
She also "wanted to get out and do things".
"I was young and headstrong and had no ideas of just being an old-fashioned wife," she said.
One of her first affairs was with Averell Harriman, an American politician and businessman who had arrived in London in March 1941 to administer the $42 billion Lend-Lease military aid program.
A shrewd, resourceful "lothario" of vast wealth, Harriman held the keys to American planes, ships and weapons and was considered a powerful ally to have on the Churchills' side.
Pamela, 30 years younger than the American, "seduced him and made sure that he knew exactly what Britain most needed … [while] at the same time she was extracting important information from him about the thinking in the White House," Purnell says.
She would then make her way back to Churchill, exchanging the information she learned on what the Americans were thinking during late-night card games with the prime minister.
The usefulness of this information, and Pamela's motives, divides opinion. Her critics dismiss her as a lightweight and cast doubt on her impact.
But it's Purnell's view that Pamela served as an "intelligence conduit" between London and Washington during the war, performing a "patriotic duty" during a desperate time.
Others, like history professor and author Frank Costigliola, write that Pamela was impelled by "self interest as well as affection" when she developed flirtatious friendships with powerful Americans.
That list included broadcaster Edward R Murrow; Major General Fred Anderson, commander of the American bombing force; media tycoon Bill Paley; and John Hay (Jock) Whitney, later US ambassador to Great Britain.
Many of these men were married at the time, "their wives thousands of miles away in America", Purnell says.
"[Pamela] made the Americans feel that she had their interests at heart," she adds.
But when the war ended, so did the need for information. As Europe prepared to rebuild, the Churchills lost office and Pamela filed for divorce from Randolph on the grounds of desertion.
With little left for her in London, she moved to France in 1949 to start her next project.
Pamela becomes a doyen of the Democratic party
In Paris, Pamela had her pick of glamorous social circles thanks to her celebrity status and last name.
''I wanted to discover a lot of things that I had not done at the age of 19," she said.
Untethered by marriage, her rambunctious private life continued, featuring an assortment of international men.
There was a fling with Prince Aly Khan, the playboy son of the Aga Kahn, and a romance with the Italian industrialist Gianni Agnelli.
They were together for five years as he tried to rehabilitate Italian automobile manufacturer Fiat's image after the war, but the couple never made it down the aisle.
An affair with Baron Elie de Rothschild, guardian of a banking dynasty, followed and, when that ended, Pamela moved to America where she married Leland Hayward, the renowned Broadway agent and producer.
They were together for 11 years until he died in 1971. That same year, a neighbour invited Pamela to a party where Averell Harriman also happened to be in attendance.
Thirty years after their wartime affair, the two widowers reunited across the pond and married.
It marked Pamela's second act, this time as doyen of the Democrats.
Harriman was a prominent fixture in America's political scene, having been elected governor of New York and serving as a top adviser to presidents John Kennedy and Lyndon Johnson. He'd also twice run for president.
With his influence and Union Pacific Railroad fortune, he and Pamela raised millions for the Democratic party's coffers through a political action committee nicknamed PamPAC.
"American by choice and a Democrat by conviction," Pamela pursued her new role with gusto, even after Harriman's death in 1986.
Time Magazine reported that a one-day fundraiser in 1992, held by Pamela at her Virginia estate, garnered more than $US3 million for her preferred candidate, Bill Clinton.
"Basically, I'm a backroom girl. I've always said this and I've always believed it. I prefer to push and shove other people. I don't really like to be put forward myself," she said.
Clinton was elected in 1992, after a 12-year campaign by the Harrimans to reinvigorate the party after its dismal defeat to Ronald Reagan.
In return, Clinton showed his gratitude by offering Pamela her first public position as US ambassador to France.
Final years spent 'splendidly' doing something 'on her own'
Paris was the backdrop to Pamela's final years. As a diplomat, she flourished in the city she once called home.
At the age of 76, she was perhaps the busiest she'd ever been, working 16-hour days on issues of international trade, the war in Bosnia and NATO.
"She finally did something so splendidly on her own … She waited so long for it. And then it was curtailed by her health," Purnell says.
On February 5, 1997, Pamela was swimming at the Ritz Hotel, not far from the apartment she once stayed in as a Churchill, when she went limp in the water.
Despite efforts to revive her, she suffered a cerebral haemorrhage and died.
Then French president Jacques Chirac paid tribute to her as a "peerless diplomat" and conferred France's highest distinction, a Grand Cross of the Legion of Honor, putting her in the same company as Thomas Jefferson and Abraham Lincoln, both former American ambassadors.
At her funeral in the National Cathedral in Washington, DC, Clinton delivered the eulogy and said he was president "in no small part because of her".
But there were still whispers that "she was nothing but a red-headed tart" and a "widow of opportunity".
"There's still a presumption that a woman could simply not have been that influential, that she was just a red-haired tart, a stealer of other women's husbands," Purnell says.
The author has herself raised eyebrows for her depiction of Pamela, particularly her account of the aristocrat during the war years with the Churchills.
She admits she would never claim Pamela was a saint.
"But she certainly changed the world for the better," Purnell adds.
