He entered the Twinings tea business at the age of fourteen with his mother after the death of his father in 1762, and succeeded to sole management in 1782 (joined later by his brother John).
[1] He participated in the major development of the tea trade caused by the operation of Commutation Act in 1784–6, during the drafting of which William Pitt the Younger repeatedly consulted him.
He had published three papers of Remarks on the tea trade of the company, and one of his first acts was to carry a self-denying motion prohibiting directors from trading with India; he took a prominent part in the affairs of the court until his resignation in 1816 in consequence of poor health.
The eldest son, Richard Twining (1772–1857), born on 5 May 1772 at Devereux Court, Strand, was educated under Samuel Parr at Norwich grammar school, and in 1794 entered the tea business, where he worked until within five weeks of his death on 14 October 1857.
John Smythies, on 5 May 1802, he had nine children, of whom the eldest son, Richard, succeeded to the business, and edited his grandfather's and granduncle's correspondence.