Born at Hoxton Old Town London, his parents were Daniel O'Brien, a cabinetmaker, and Ann O'Brien. Thomas came to Australia, visiting the Victorian goldfields in 1863 with a brother, but returned to England a year later and worked at his trade of
stonemason. He dropped his father's surname by the time of his marriage to Jane Harriett Strew on 21 November 1869. Spencer was elected vice-president of the
Stonemasons' Society of London, and assisted its president
Henry Broadhurst in the settlement of industrial disputes. Spencer migrated to
Sydney, Australia in 1875 and became a successful builder and contractor, winning government contracts for work on Goulburn gaol, the
University of Sydney's physics laboratory and the sewerage system in Sydney. Spencer's wife died in 1880, leaving a son aged 7. On 6 April 1882 at
Goulburn, Spencer married Sarah Ann Christie. During his latter years, Spencer spent much of his time as an arbitrator in industrial disputes. From 1907 to 1911 he presided over many wages boards, and his experience and sense of justice enabled him to do valuable work. Spencer died at
Sydney on 6 May 1911, leaving a widow, their two sons and two daughters, along with a son from his first marriage. Spencer was buried in the Anglican section of
Rookwood Cemetery. == Writing career ==