Over a decade before Margaret Thatcher swept to power, another woman was running Britain from 10 Downing Street: Marcia Williams was the first ever female political adviser to a Prime Minister and was said to have a powerful grip on her boss.

Historians have described the relationship between Marcia and Labour Prime Minister Harold Wilson as one of the most famous but mysterious partnerships in modern political history. A brilliant tactician, Marcia masterminded Wilson's multiple election victories. Indeed, he said that but for her ingenuity, he would never have become Prime Minister.

But misogyny, jealousy, a shocking private life and accusations of money-grubbing and bribery all contributed to her reputation as a public nuisance. Marcia's young and ambitious male colleagues said she humiliated and screamed at Wilson, single-handedly ruining his chances of being remembered as a 'great' Prime Minister.

There is no doubt Marcia was outspoken, forthright and, by contemporary standards, deeply unconventional. But her critics failed to understand her unbreakable partnership with Wilson they were politically wedded to each other and equal contributors to his success.

'It was a mesmerising moment in British political history and McDougall is absolutely right to revise Marcia's reputation.' Daily Telegraph

'This insightful study puts her back where she belongs at the forefront of politics.' Daily Mail

'Linda McDougall gives an infinitely more nuanced and sympathetic picture of this extraordinary woman. I found her biography gripping with its in knowledge of government, its picture of the emotional dynamics of Downing Street and its sensational claim that Marcia might have been drugged by Wilson's own doctor.' Anne de Courcy, The Spectator

'McDougall has succeeded in writing a kindly biography of a woman not many have been kind about.' Literary Review