Benn was born in
Manchester, to a middle-class family, the eldest son of a
Congregationalist minister, the Reverend Julius Benn (c. 1826–1883), and grandson of
Cheshire quilting manufacturer William Benn, but his parents moved the family to east
London the following year, where they opened an institute for homeless boys. Benn was largely homeschooled and at the age of seventeen, he joined a
furniture company. He later (1880) established a trade journal,
The Cabinet Maker, which eventually became the furniture trade's leading publication: when politics became his main interest, the family's publishing business, Benn Brothers, was taken over by his eldest son
Ernest Benn (1875–1954), who later renamed it
Ernest Benn Limited. His niece was actress
Margaret Rutherford; she was the daughter of Benn's younger brother
William Rutherford Benn, who was put into a lunatic asylum following his murder of their father, the Rev. Julius Benn. When the
London County Council was established in January 1889, Benn accepted an invitation to stand as a
Progressive Party candidate for
East Finsbury and was elected. Like his contemporary
Will Crooks, Benn was active in the
London Dock Strike of 1889, and, as an increasingly prominent local politician, was invited in 1891 to stand for Parliament as the
Liberal Party candidate for
St George Division of Tower Hamlets. He won election from the constituency
the following year. He was later narrowly defeated at the
general election in 1895, but he concentrated on his continuing work as a London councillor, helping introduce electric
trams to London's streets in 1903. A year later, he returned to Parliament after winning a
by-election at
Devonport, a seat he retained until being defeated in 1910. In the meantime his son, 28-year-old
William Wedgwood Benn, had also been elected to Parliament, winning Benn's former seat at St. George in 1906. Benn senior was appointed a
deputy lieutenant of the
County of London in February 1905. For his work as an MP, he was knighted in 1906 and created a
baronet in 1914. John Benn remained a member of the London County Council until his death in 1922, leading the Progressive Party until ill-health forced him to relinquish that role in 1918. In his final election campaign he was victorious, defeating the Labour Group Leader. ==Arms==