This first film looks at the period between the 1900s and the late 1950s, an era when the ideal of romantic love in marriage had to withstand the harsh realities of a world very different to today. Yet many marriages were defined by friendship rather than conflict and strife. Above all else couples wanted to provide a stable and loving home for their children - even those who struggled to bring up large families on the breadline. Despite the tragedy of two world wars, most marriages not only survived - some became even stronger. Hetty Bower, now 107 and Britain's oldest peace campaigner, tells the moving story of her love and marriage to husband Reg Agony aunt Denise Robertson is emotional as she recalls how her parents remained passionately in love, despite losing everything in the economic crash of the 1930s. They provided an inspirational role model for her of a successful marriage.

In the 1960s and 70s the traditional ideals of marriage were questioned as never before. These were decades of greater affluence, optimism and experimentation, in which rebellious youth was in the vanguard of a cultural revolution. One of the archetypal feminist rebels of this period was Rosie Boycott and the co-founder of Spare Rib describes why she once rejected marriage and how she lived the 'sex, drugs and rock 'n' roll' lifestyle to the point of self-destruction. The sexual experimentation of the period is captured by Anne Geraghty and Martin Gerrish, who joined the Orange People and lived in free love communes, but ended up marrying each other. Divorce was on the increase during the 1960s and 70s, made possible by divorce law reform. Convent girl Maureen Flanagan married an Irish navvy who resented her career as a model, and when she became the Sun's first Page Three girl their marriage was over.

The effects of the sexual revolution, the empowerment of women and the growth of a global consumer society based on individual choice were only fully played out in the last decades of the 20th century, when the divorce rate increased to an all-time high of one in three marriages. This final episode explores how marriage has adapted to these pressures by looking at the ups and downs of five couples whose relationships personify modern marriage. It looks at the mixed-race marriage of Mo and Ann Chaudry and their rags-to-riches journey which resulted in a millionaire lifestyle and a happy family. Kate and Harry Benson had a glamorous Lady Di-style wedding but their marriage almost followed suit, nearly ending in divorce. They both became marriage guidance counsellors and Harry now heads up the new Marriage Foundation. Rock stars Toyah Wilcox and Robert Fripp reveal their romantic love story, their ups and downs and how they have kept their 25-year marriage strong.