Edith Ruth Thomas, the daughter of David Collet Thomas, merchant and shipowner, was born in born Highgate in 1858. After finishing her education she did social work in Bethnal Green. This experience radicalised her and she was a founder member of the Anti-Sweating League.
On 20 August 1885 she married Charles Mansell-Moullin, as assistant surgeon at London Hospital. The couple had similar political views. Both were socialists and supported the campaign for women's suffrage. This included being members of the Church League for Women's Suffrage and the Church Socialist League.
Edith Mansell Moullin helped establish the Cymric Suffrage Union. As Angela V. John has pointed out: "Small, dark-haired, and passionate in her commitments, she did not draw neat distinctions between her public and personal life. Typically, the family's home in fashionable Wimpole Street was the society's headquarters. There were a few branches in Wales and she went on several speaking tours in north Wales."
By 1903 Emmeline Pankhurst had become frustrated at the lack of progress towards women's suffrage. With the help of her three daughters, Christabel Pankhurst, Sylvia Pankhurst and Adela Pankhurst, she formed the Women's Social and Political Union (WSPU). As an early member of the WSPU, Dora Montefiore, pointed out: "The work of the Women’s Social and Political Union was begun by Mrs. Pankhurst in Manchester, and by a group of women in London who had revolted against the inertia and conventionalism which seemed to have fastened upon" the NUWSS.Edith Mansell Moullin joined the WSPU. Men were not allowed to join the organisation but in 1907, several left-wing intellectuals, including Charles Mansell-Moullin, Henry Nevinson, Laurence Housman, Charles Corbett, Henry Brailsford, C. E. M. Joad, Israel Zangwill, Hugh Franklin, Charles Mansell-Moullin and 30 other men formed the Men's League For Women's Suffrage "with the object of bringing to bear upon the movement the electoral power of men. To obtain for women the vote on the same terms as those on which it is now, or may in the future, be granted to men." Evelyn Sharp later argued: "It is impossible to rate too highly the sacrifices that they (Henry Nevinson and Laurence Housman) and H. N. Brailsford, F. W. Pethick Lawrence, Harold Laski, Israel Zangwill, Gerald Gould, George Lansbury, and many others made to keep our movement free from the suggestion of a sex war."
In November 1911, Edith Mansell Moullin, was one of the main speakers at the Caxton Hall meeting which preceded a demonstration in Parliament Square. She was one of 223 arrested. Charged with trying to break through the police cordon, she denied attempting to disturb the peace, claiming that the police were obstructing her. She spent five days in Holloway Prison before being released.
Sylvia Pankhurst, argues in her book, The Suffrage Movement (1931) that Mansell Moullin along with George Lansbury, Henry Nevinson and Evelyn Sharp organised a protest meeting at Caxton Hall when she was arrested in June, 1914.
On 4th August, 1914, England declared war on Germany. Two days later the NUWSS announced that it was suspending all political activity until the war was over. The leadership of the WSPU began negotiating with the British government. On the 10th August the government announced it was releasing all suffragettes from prison. In return, the WSPU agreed to end their militant activities and help the war effort.
Emmeline Pankhurst announced that all militants had to "fight for their country as they fought for the vote." Ethel Smyth pointed out in her autobiography, Female Pipings for Eden (1933): "Mrs Pankhurst declared that it was now a question of Votes for Women, but of having any country left to vote in. The Suffrage ship was put out of commission for the duration of the war, and the militants began to tackle the common task."
Edith Mansell Moullin was a pacifist so she completely disagreed with this strategy. She therefore left the Women's Social and Political Union and instead became a supporter of the Women's Freedom League. Edith believed that the British government did not do enough to bring an end to the war and between 1914-1918 supported the campaign of the Women's Peace Crusade for a negotiated peace. She also launched an appeal to help thirty-six Welsh wives of imprisoned Germans who had been working in Welsh mines. The wives were not receiving relief as they were not considered to be British subjects.
After the war Edith campaigned for world peace. She was involved with the Society for Cultural Relations with the USSR and in 1931 became its chairman. She was also a voluntary helper at St Dunstan's in Brighton, a home for blind servicemen.
Charles Mansell Moullin died aged eighty-nine in 1940. Edith died the following year on 5th March at 2 Cottesmore Court, Stanford Road, Kensington, the home of her only child, Oswald.