Apprenticed to a Woolwich shipwright aged 14, afterwards Bentham spent some time working on nautical studies in Portsmouth. During this period, he suggested various improvements in shipbuilding and fitting which were well received. Unable nonetheless to find satisfactory employment he decided to study foreign shipbuilding and sailed to Russia in 1780, where he travelled widely. He declined a British commissionership in 1783 in order to remain in St Petersburg and was sent by Prince Potemkin to Cherson as a Lieutenant-Colonel. Subsequently he was occupied in shipbuilding and it is said that his ideas for the layout of his works inspired the Panopticon of his brother Jeremy.
He was awarded the cross of St George for his work arming boats for an engagement with the Turks in 1787-88. (Later, after an audience with the English King, he assumed the 'Sir' on the basis of being a Knight of the Russian order of St George, never having been officially knighted.)
In 1791 Bentham returned to England, resigning his Russian responsibilities in order to work for the Admiralty. Over the next two decades he rose to become Inspector-General of the Navy Works. During this time in England he was responsible for the introduction of Brunel's immensely successful blockmaking machinery at Portsmouth and installing breakwaters in docks.
However, in trying to cure the malaise afflicting the administration of the dockyards Bentham made various enemies. In 1805 he was 'exiled' to St Petersburg, and on his return informed that his position had been abolished. He continued to work for the navy, having a number of sound suggestions blocked. In 1814 he moved to France, returning to England a few years before his death in 1831.