One of the better known artists of the Norwich School. He was born in Norwich, became an apprentice frame-maker in London, and around 1800 established himself back in Norwich as a printmaker and framer. He married the sister in law of John Sell Cotman, and was influenced by him and by John Crome, becoming a significant watercolourist. From 1805 he sent pictures to the Norwich Society of Artists, and became President of that body in 1814. However, in 1816, along with other artists, he broke away to form a rival group, which survived until 1818. He resumed exhibiting at the Society only belatedly in 1828. He also exhibited a single picture at the Royal Academy, in 1808.
Thirtle's output consisted of rustic and river scenes in watercolour, set in the vicinity of Norwich. Unfortunately, his much-favoured indigo blue paint turned red over time, leaving some of his pictures with a rather ruddy tint.
Paintings by Thirtle may be seen at the Norwich Castle Museum.