Turning the Tide: The Life of Lady Rhondda, By Angela V John: Book review - a Welsh wonder who rode the first waves of feminism

Margaret, Lady Rhondda, was an improbable revolutionary. A socially elitist millionaire who lived next to the Ritz, she threw herself, and her money, into promoting women's equality in politics, in print and (briefly) in gaol. Angela John's excellent biography is thus to be welcomed warmly.

Margaret was, above all, her father's daughter. D A Thomas, Lord Rhondda, was a Welsh Rockefeller – tsar of the coalfield, long-term Liberal MP and food controller during the First World War. Margaret inherited his empire of mines, shipping and newspapers to become "the foremost woman of business in the British Empire", sitting on 33 boards, and in 1926 becoming the first (and only) female president of the Institute of Directors.

Her wealth was eroded in the Depression, but she invested heavily in her good causes, above all the weekly Time and Tide magazine she launched in 1920 to promote the causes of women. Remarkably, its management and editors were all female. Later on, it took a pronounced literary turn and became a platform for Shaw, TS Eliot and Virginia Woolf among others.

Lady Rhondda's supreme campaign was an elitist one – pressing her right, after inheriting her father's title, to take her place in the House of Lords. After backing from the Committee of Privileges, her campaign was blitzed by Lord Birkenhead, whose learned legal pronouncements masked prejudice of the most primitive kind. Margaret's 30-year campaign foundered – although, ironically, just before her death in 1958, women were enabled to enter the Lords under the Life Peerages Act.

Margaret's feminism made enemies, Vera Brittain being one. She had stressful relationships with her editor, Helen Archdale, the novelist Winifred Holtby, Eleanor Rathbone, and her one real Labour friend, "Red Ellen" Wilkinson. Her feminism seemed repelled by marriage and the maternal instinct and she fretted over "that perpetual, unsatisfied sex-hunger" among young women.

But she was a courageous pioneer, who faced down prejudice in business, politics and the press. She exposed gender discrimination everywhere, and shared in major victories such as the vote being extended to all adult women in 1928. Today's House of Lords not only contains nearly 200 women, and a female Lord Speaker – it also contains Margaret herself, since her portrait now hangs in the peers' dining room. "Lady Roundabout" presides over a living legislature, while the prejudices of Lord Birkenhead fester in the dustbin of history.