Holt was the son of a Yorkshire wool merchant and was educated in Wakefield. He initially worked in his father's firm in Leeds but after 3 years became a wool buyer in London. Subsequently, Holt emigrated to Sydney in 1842 and made a fortune as a wool merchant. He was also a director of numerous colonial companies including the Sydney Railway Company. Holt invested extensively in pastoral land and by 1860 had acquired more than in New South Wales and Queensland. As a result, he was independently wealthy and retired from active business in 1855. After building a gothic stone mansion, "The Warren", on land overlooking the Cooks River in Marrickville, Holt stocked the grounds with imported European rabbits for breeding and hunting, alpacas, llamas and salmon. Holt also had an extensive estate in the Sans Souci area of Sydney. In later life he was a founder of Royal Prince Alfred Hospital, a member of the Royal Society of New South Wales and a patron of the Royal Agricultural Society of New South Wales.
Colonial Parliament
Holt was unsuccessful at two attempts to enter the Legislative Council prior to the establishment of responsible self-government in 1856. However, at the first election under the new constitution he was elected to the Legislative Assembly as one of the two members for Stanley Boroughs which, prior to the establishment of Queensland as a separate colony in 1859, was part of New South Wales. At the next election in 1858, Holt was defeated in an attempt to transfer to the seat of Cumberland. He re-entered the Assembly as the member for Newtown at an 1861 by-election caused by the resignation of Alexander McArthur but resigned from the seat before the next election in 1864–65. In 1868 he accepted a life appointment to the Legislative Council. Holt was a supporter of free-trade and had a liberal political philosophy. Throughout his political career he campaigned for education, gaol and immigration reform and spent a small fortune supporting Henry Parkes' "Empire" newspaper. An active Congregationalist, in 1864 he gave half the value of his residence, Camden Villa, towards the founding of Camden College.
Government
Holt was New South Wales' inaugural Colonial Treasurer in the liberal government of Stuart Donaldson. He held this position for 81 days.
Later life
In 1881 Thomas went back to England where he devoted himself to the poor of London, working with The Salvation Army, the Rev Andrew Mearns, and Dr Barnardo. He died at his home "Halcot" in Bexley, Kent, on 5 September, after completing his book, 'Christianity, or the Poor Man's Friend'; and was buried at Abney Park Cemetery.
Legacy
The Thomas Holt Retirement Villages in the south of Sydney are named after him.
