Thomas Downes Wilmot Dearn was born 12th April 1777 in London and christened at St. Clements Danes in the Parish of Westminster on 9th June by his adopted parents Thomas Dearn and Eleanor Wilmot. He grew up unaware of his real parentage until in 1803, at the age of 26, his uncle Temple Simon Luttrell told him of his real (royal) parentage and the existence of his sister Olive who had been adopted as well. Dearn had married Elisabeth Stevenson at St. Dunstan's Church, Cranbrook on 20th November 1800. They had a family of two daughters, Ann and Elizabeth, before they were requested to adopt his sister Olive's daughter, Caroline in 1805. Ten years were to elapse before Thomas and Elisabeth were to have the rest of their family.

Thomas Dearn had moved to Cranbrook in the mid 1790s and quickly became a prominent member of the Cranbrook community. From 1809 until 1843, he was prolific producer of prints of topographical and architectural images and maps for Cranbrook and the surrounding area - almost 100 in total. From 1798 until 1828 he regularly had architectural exhibits at the Royal Academy. As an architect he is attributed with the design of numerous properties in the Cranbrook area including his own house Dearn Villa. He published a number of books on architecture culminating in his 'Designs for Lodges and Entrances to Parks, Paddocks and Pleasure Gardens' in 1811. However, it was his book An Historical and Descriptive Account of the weald of Kent, published in 1814 that was to gain him real prominence and popularity.

Thomas Dearn lived to be 76 when he died on 17th January 1853. He is buried at St Dunstan's Church in Cranbrook

The circumstances surrounding Thomas Dearns' parentage, his early life and his life as an author, artist and architect in Cranbrook are depicted in the definitive biography of him, 'Sporting the Oak' by Paul Donovan and published in 2005