R. Glynn Grylls was the pen name of Rosalie Glynn Grylls, born in England to an ancient Cornish family. She attended Queen's College, London and graduated from Oxford University. In 1930, she married as his second wife Geoffrey Le Mesurier Mander, a Member of Parliament nearly 20 years her senior, with whom she had two children. That same year, she was selected as the Liberal Party candidate for Reading for the General Election of 1931; however, the Liberals later decided not contest the seat. She continued to be interested in progressive politics, but did not attempt to stand again for public office. She became a writer and noted biographer with a special interest in the Romantic period and the Pre-Raphaelite movement. Her biographical subjects included Mary Shelley (1938), Claire Clairmont (1939), Edward John Trelawny (1950), William Godwin (1953), Dante Gabriel Rossetti (1964), and Elizabeth Barrett Browning (1980). She lectured frequently on these writers and artists in the USA. In 1945, after her husband was knighted, she was known as Lady Mander.