Megan McDonough is a weddings and obituary writer for the Washington Post.

Much has been written about Winston Churchill but relatively little about his principal counselor and most-trusted confidante, his wife, Clementine. Now, more than 60 years after their departure from 10 Downing St., biographer Sonia Purnell explores how Clementine Churchill, a Victorian-age woman “who never went to university, had five children and could not vote until her thirties,” became one of the most influential, powerful and progressive first ladies of Britain.

In Purnell’s telling, there is little chance that Winston Churchill would have flourished, let alone become prime minister, without his wife’s unwavering support.

“She was, in effect, an early twentieth-century amalgam of special adviser, lobbyist and spin doctor,” Purnell observes.

As Winston Churchill’s formidable counterpart for 57 years, Clementine devoted her life to furthering her husband’s well-being and political ambitions, often at the expense of her own — and their children’s — desires, health and happiness. She not only offered wise counsel and rewrote his speeches, but once “leaped in a flash over piles of luggage” to save him when he was pushed in front of an oncoming train.

"Clementine: The Life of Mrs. Winston Churchil" by Sonia Purnell (Viking)

But unlike her American counterpart Eleanor Roosevelt, Clementine Churchill was less concerned with becoming a political force in her own right. She carefully operated behind the scenes and never contradicted her husband in public. She used her influence, keen political intellect and positive public persona to boost morale on the home front and help cement positive relations with America. She “became the human face of Winston’s government” and “was looked to as someone who could get things done,” Purnell writes.

Consumed with her husband’s career, she subordinated her role as a mother, too. She spent little time with her children. As their daughter Mary said, “Father always came First, Second and Third.” Decades later, Clementine Churchill would express regret for her neglect, remarking to Mary, “You have so much fun with your children that I now realise how I missed out.”

Purnell’s thorough and engaging account looks back at the early forces that shaped Britain’s beloved first lady. Born Clementine Hozier, the future Mrs. Churchill’s childhood was marked by scandal and sadness, including the death of her older sister from typhoid fever at age 17. Her parents became estranged, and her mother, a notorious philanderer and compulsive gambler, was emotionally distant. At 19, Clementine met Winston Churchill, 10 years her senior, at a ball in London. Four years later, they were reacquainted at a dinner party. Several months later, they were married.

Together, the Churchills steered Britain through war and sometimes rocky political waters. They also shared moments of personal tragedy, including the loss of their third daughter, Marigold, at age 2.

The Churchills’ busy life kept them apart a great deal — by one estimate, Clementine spent 80 percent of her marriage without her husband. But according to Purnell, the couple nonetheless managed to maintain a deeply affectionate and passionate relationship, corresponding almost daily with letters. In these, Winston revealed his unabashed love for, and dependence on, his wife. “[My] greatest good fortune in a life of brilliant experience has been to find you, & to lead my life with you,” he confided. “I feel that the nearer I get to honour, the nearer I am to you.”

Purnell’s extensive and insightful biography offers a much welcome portrait of Clementine Churchill, a woman whose remarkable life has long been overshadowed by her famous husband. As Purnell writes, “Of all the influences in his life she was the most woefully unappreciated — but in truth she was the strongest.”

The Life of Mrs. Winston Churchill

By Sonia Purnell

Viking. 436 pp. $30