One woman, more than any other, bulldozed the British establishment into allowing this revolution. She was Dr Marie Stopes who, from June Rose's biography, comes across as one of the most colourful characters of this century.

During World War I, Stopes wrote her most important book, Married Love, the country's first frank guide to fulfilment in sex and marriage and choice in child-bearing. Hundreds of sex manuals may have followed, but she was writing at a time when biology books still omitted reproductive organs from their illustrations and when conservatives advocated the diversion of more drill halls and tea-houses to control excessive breeding.

The ground-breaking book was followed up with specific guides to contraception and practical help in the form of the first birth control clinics opened in the then British Empire.

For Stopes, the status of women was not an issue. Born in 1880, she was brought up in a blue-stocking environment where women were naturally superior. In all her relationships, except with her mother, she was the domineering, if not overpowering force. While there were others working to promote birth control, it took her extraordinary personality to raise the issue beyond the mere academic level.

Ms Rose's highly readable and balanced biography intertwines the story of the woman with this vital chapter in modern social history.

As a campaigner and pioneer Stopes' single-mindedness, confidence and vivacity were her greatest assets. But as a person, these qualities made her increasingly insufferable while her dogmatism and egotism finally made her redundant to the very movement she initiated.

One of the most interesting parts of Ms Rose's book is how Stopes, whose useful ''doctor'' title derived from her German PhD in paleobotany rather than any medical training, came to cast herself as birth control pioneer and agony aunt.

Throughout her life Stopes was an incurable romantic in search of ultimate love. As a young graduate her heightened romanticism led her to follow a Japanese professor she was enamoured with to Japan. She poured out her emotions and sexual feelings in several unpublished novels, and in later life, volumes of second-rate romantic poetry.

It was this adolescent obsession with romance that led her to write Married Love, a guide to ideal love as shocking to many as D.H. Lawrence's Lady Chatterley's Lover would later be.

But as a vent for the sexual frustrations of a nation just pulling itself out of the era of Victorian prudery, the book was a best-seller and shot Stopes to the fame she craved for.

Contraceptive methods were only briefly mentioned in Married Love. But through her new husband and sponsor, Humphrey Roe, who had already applied to open a birth control clinic in a Manchester hospital, it was a short step for her to adopt ''constructive birth control'' as her own cause.

Unlike other birth control campaigners, such as Margaret Sanger in the US, Stopes was not motivated by any deep concern for the plight of the poor, who suffered most from the lack of birth control, but by her quest for love and good sex and a dangerouslyidealistic opinion that it would enhance the race that led the British Empire.

Indeed, she initially expected Married Love to be read only by women of similar genteel breeding and education to herself. She bore all the disdain of her class for the ''ignorant'' masses. But her sharp intellect quickly enabled her to realise and act on the wider significance of birth control.

Ironically, Stopes herself was anything but happy in married life. She rejected her first husband on the grounds that he was impotent and soon tired of her doting Humphrey. As Ms Rose says, she never learnt the two most vital ingredients of marital success - an ability to compromise and a sense of humour.

As the ultimate egotist, Stopes left a mountain of clues to her unusual life. Ms Rose brings much revealing colour to her book by quoting poems and explicit love letters.

In a letter to Humphrey his wife wrote: ''I hope my darling is being a very splendid and to-be-proud-of darling and will master everything except his little wife what loves him.'' Unlike other birth control campaigners, Stopes was not motivated by concern for the poor but by her quest for love