William Henry Allen was born in Lenton, Nottingham, Nottinghamshire, England in early 1873. He was later baptised in Coventry, Warwickshire on 30 July 1876.
He was the son of Alfred Allen (b. 1849), a turner and later a factory foreman, and Hannah Selina Hunt (b. 1851), natives of Birmingham who were married in early 1872, and William was one of their six children. His siblings were: George Alfred (b. 1874), Arthur Archibald (b. 1876), Florence Louise (b. 1878), Gertrude Miriam (b. 1887) and Elsie (b. 1893).
He first appears on the 1881 census living at 34 Leicester Street in St Mary, Nottingham followed by the 1891 census when he and his family were living at 5 Addington Road, Radford, Nottingham. His parents and two younger sisters later moved to London, settling in Hackney where they would appear on the 1901 and 1911 censuses. William apparently remained behind in Nottingham and was listed on the 1901 census as a boarder at 114 Cremorne Road in that city and was described as an unmarried engine fitter's apprentice. His landlords where Mr and Mrs Henry Rigby and one of their daughters would later become William's wife.
William was married in 1906 to Florence Ann Rigby (b. 1877 in Sandiacre, Derbyshire). The 1911 census shows William boarding at 63 Kingsway in Coventry and he was described by then as a toolmaker in the nut and screw trade. His wife was shown on the same census residing with her parents at 118 Cremorne Street, Nottingham. Contemporary media reports that by 1912 the couple, who were childless, were residing together at 78 Queen's Road, Erdington, Birmingham.
After staying with his parents for a short while at Albert Cottage, Pembury Road, Clapton, London, Allen boarded the Titanic at Southampton as a third class passenger (ticket number 373450 which cost £8, 1s). He planned to get a job in the USA whilst staying with an uncle at 593 Eleventh Avenue, New York City. He was the best friend of steward George Hinckley. Hinckley, originally of Derby, had left his job at Birmingham Metal and Munitions Co. Ltd, Adderley Park, Birmingham. It is possible that the two men had worked together.
William Allen died in the Titanic disaster and his body was never recovered. His estate worth £167, 10s which administered to his widow on 5 April 1913. Florence Allen never remarried and eventually resettled in Bridgford, Nottinghamshire. She passed away on 15 September 1965.
A suitcase belonging to Allen was recovered from the wreck in 2000. It contained clothing that bore a laundry stamp "W. Allen".