He gained a reputation as a profligate and a dandy, and in 1837, was transported to the penal colony of Van Diemen's Land (now the Australian state of Tasmania) for frauds on the Bank of England.

Wainewright's mother Ann was the daughter of Ralph Griffiths (1720–1803), for many years the editor of the literary magazine Monthly Review.

Wainewright subsequently served briefly as an officer in a yeomanry regiment, having bought his commission in 1814, but lasted just over a year, probably because of a severe mental illness.

It was suggested by the writer Havelock Ellis that Wainewright was never normal after this period of his life, when he was on the verge of or already succumbed to insanity, and this contributed to his later crimes.

He was, however, most closely linked with The London Magazine, to which he contributed articles and art criticism from 1820 to 1823, under the pen names Janus Weathercock, Egomet Bonmot and Cornelius van Vinkbooms.

He was a friend of Charles Lamb, who thought well of his writing and, in a letter to Bernard Barton, styles him "the kind, light-hearted Wainewright."

He produced a portrait of Lord Byron and made illustrations for the poems of William Chamberlayne, and from 1821 to 1825 exhibited narratives based on literature and music at the Royal Academy, including Romance from Undine, Paris in the Chamber of Helen and the Milkmaid's Song.

On two separate occasions, Wainewright forged signatures of power of attorney and withdrew large sums from the Bank of England, first in 1822 and then in 1823.

The Essays and Criticisms of Wainewright were published in 1880, with an account of his life, by W. Carew Hazlitt; and the history of his crimes suggested to Charles Dickens his story "Hunted Down" and to Edward Bulwer-Lytton, 1st Baron Lytton his novel Lucretia.

Arthur Conan Doyle also mentions Wainewright in the Sherlock Holmes story "The Adventure of the Illustrious Client" as "no mean artist", but spells his name without the middle "e".

Wainewright was the subject of the seventeenth episode of the television show Thriller, "The Poisoner" (aired 10 January 1961), with Murray Matheson playing the role of the killer (given the fictional name Thomas Edward Griffith) and featuring Sarah Marshall as his wife.