John William Stephens was born around 1861 in Attleborough, near Nuneaton, Warwickshire, the son of Joseph, a ribbon weaver, and Sarah Ann, who died in 1864 on William Street in Derby at the age of twenty-five from spinal disease, leaving John at about three years old. By 1871, Joseph had remarried a woman called Ruth and moved the family to Leicester, where John grew up as a scholar on Calais Street.

In December 1877, aged around sixteen but claiming to be twenty, John enlisted in the Royal Artillery at Birmingham as a labourer. He served in Mauritius and Natal during the Anglo-Zulu War of 1879, earning a campaign medal with clasp, and remained in South Africa for several years, marrying Sarah Ann Cooke in Cape Town in January 1883. Two children, Edith and William Thomas, were baptised at the Garrison Chapel that same year.

Discharged in December 1889 John joined the Leicester Borough Police and served for twenty-two years as a constable, never once promoted. Stationed on point duty at the Clock Tower, he became famous as the heaviest serving policeman in England, officially weighed at twenty-three stone and two pounds in 1905, earning the nickname "Tubby." Picture postcards were produced of him, and he was known for his good humour, particularly his habit of moving loiterers along with his stomach while asking, "Do you play chess? Well, it's your move."

John died on 4th April 1908 at 84 Cobden Street, Leicester, aged forty-seven, from heart failure and bronchial asthma. His stepmother Ruth, who had been in his life since he was a child, was present at the death. His funeral on 8th April drew an estimated ten to twenty thousand mourners, and his coffin had to be removed through a window. He was buried in an unmarked grave at Welford Road Cemetery, which was finally given a headstone by the Leicestershire Police Federation Trust in 2017.