The Hon. Margaret Haig Thomas was the only daughter of David Alfred Thomas, 1st Viscount Rhondda, and his wife Sybil. She attended Notting Hill School and St. Leonard's, and then went up to Oxford University for a year. In 1908, she married Sir Humphrey Mackworth. She joined the Women's Social and Political Union and became a militant suffragist. She was arrested after attempting to blow up a postal box as part of the WSPU's arson campaign. Margaret was sent to prison, where she went on a hunger strike that led to her release. She accepted the WSPU's truce with the British government during World War I, and was employed by the War Office as a food controller. She was aboard the Lusitania when it was torpedoed by a German submarine in 1915, but was rescued. On her father's death in 1918, Margaret became Viscountess Rhondda. She founded the political magazine Time and Tide in 1920, and edited it until her death. Lady Rhondda and her husband divorced in the 1920s, and she set up home with Helen Archdale, a fellow suffragist. She published a Life of her father in 1921, and was the author of several volumes of memoirs entitled Notes on the Way and This Was My World (1933). Her portrait was painted by Alice Burton in 1932.