For Valentine's week, the Poet Laureate, Carol Ann Duffy, explores the heady world of love poetry from first flush to final parting. In conversation with other love poets, Carol Ann celebrates the great poems of love and explores poets' responses to love's mysteries. Each of the five programmes in the series looks at a different stage in the development of a relationship. Today's episode explores poems that commemorate the making of vows, including the world's oldest love poem. Presented by Carol Ann Duffy. Produced by Emma Harding.