In January 1908 Elsie Duval was sentenced to one month's imprisonment after taking part in a demonstration at the home of Herbert Asquith. In 1911 Emily Duval left the WFL because it was not militant enough and rejoined the WSPU. Elsie's father, was also a supporter of women's suffrage and was a member of the Men's League For Women's Suffrage. Her brother, Victor Duval, was also imprisoned several times for taking part in demonstrations.
Elsie Duval joined the WSPU at the age of fifteen. She was at first too young to be involved in militant activity and was not arrested until 23rd November 1911 on a charge of obstructing the police. In March 1912 the WSPU organised a new campaign that involved the large-scale smashing of shop-windows. Elsie took part in this campaign and in July was sentenced to a month's imprisonment for breaking a window in Clapham. While in prison she was forcibly fed nine times.
Duval also took part in the WSPU's arson campaign. It is believed she was responsible for burning Sanderstead Station. She was arrested for "loitering with intent" on 3rd April 1913. She was sentenced to one month's imprisonment. After being released under the Cat and Mouse Act, she escaped with her boyfriend, Hugh Franklin, to Belgium and stayed in Brussels. She received a letter from Jessie Kenney that said: "Miss Pankhurst thinks it would be better for you to stay where you are for the time being and until you get stronger."
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. Duval and Franklin now returned to England.
During the First World War she applied to work with Louisa Garrett Anderson and Flora Murray in a hospital in Claridge Hotel in Paris. The offer was rejected and on 28th September 1915 she married Hugh Franklin in the West London Synagogue. His father disinherited him for marrying out of the Jewish faith and never saw him again.
Elsie Duval became ill during the influenza epidemic and died of heart failure on 1st January 1919. It is believed that her heart had been weakened by the treatment she received in prison.