[1] Sexton was born in Newcastle upon Tyne on 13 April 1856 to an Irish-born family of market traders,[2] who shortly afterwards moved to a slum area of St Helens, Lancashire.

He grew up in poverty and began work in the local glass-making industry at the age of nine after briefly attending school.

Sexton eventually wandered to Liverpool, where he worked as a sailor, then arrived in London after deserting the ship he was sailing on and took a job at a chemical factory.

While working as a dock labourer he was extremely distraught by the living conditions of himself and his colleagues which were brought upon them by their wealthy bosses.

During this time, Sexton also became active in the Irish Home Rule movement, however he ceased participating in it shortly after the Parnell split.

He stood unsuccessfully for Liverpool West Toxteth in the 1906 general election and then served as Labour Member of Parliament for St Helens from 1918 to 1931.