John Thelwall is best known for his political activism during the French Revolution and he is among the few British Romantics who wrote Arthurian literature.

Thelwall's attempts to become an artist were thwarted by financial difficulties. For a short time he went to college to learn historical painting, returning home when his father died. To support his family, he worked as a shopkeeper. Meanwhile he read constantly and kept a candle in his pocket so he could continue reading while walking at night. He made an unsuccessful attempt at acting by converting the shop into a stage to perform The Tragedy of Barbarossa. Once his interest in business had completely waned, he began to study divinity with his brother-in-law to become educated enough to be a lawyer's assistant. He was a copier for John Impey in 1782 and quickly left that profession.

In 1787 Thelwall published his first book, Poems upon Various Subjects, which was favorably reviewed by Critical Review. Riding on this literary success, he became the editor for Biographical and Imperial Magazine. Also, he conducted and spoke regularly in public debating societies. A few years later he married Susan Vellum who financed his literary and political ventures. During this time he met many important Romantic literary figures: Robert Southey, William Wordsworth, Samuel Taylor Coleridge, William Hazlitt, Charles Lamb, and Crabb Robinson.

During the French Revolution Thelwall was an outspoken member of the London Corresponding Society advocating radical, Jacobin politics. He publicly criticized the government for waging a war against France and thereby causing a financial drain directly affecting working and lower classes. Noting Thelwall's attention

John Thelwall is best known for his political activism during the French Revolution and he is among the few British Romantics who wrote Arthurian literature.

Thelwall's attempts to become an artist were thwarted by financial difficulties. For a short time he went to college to learn historical painting, returning home when his father died. To support his family, he worked as a shopkeeper. Meanwhile he read constantly and kept a candle in his pocket so he could continue reading while walking at night. He made an unsuccessful attempt at acting by converting the shop into a stage to perform The Tragedy of Barbarossa. Once his interest in business had completely waned, he began to study divinity with his brother-in-law to become educated enough to be a lawyer's assistant. He was a copier for John Impey in 1782 and quickly left that profession.

In 1787 Thelwall published his first book, Poems upon Various Subjects, which was favorably reviewed by Critical Review. Riding on this literary success, he became the editor for Biographical and Imperial Magazine. Also, he conducted and spoke regularly in public debating societies. A few years later he married Susan Vellum who financed his literary and political ventures. During this time he met many important Romantic literary figures: Robert Southey, William Wordsworth, Samuel Taylor Coleridge, William Hazlitt, Charles Lamb, and Crabb Robinson.

During the French Revolution Thelwall was an outspoken member of the London Corresponding Society advocating radical, Jacobin politics. He publicly criticized the government for waging a war against France and thereby causing a financial drain directly affecting working and lower classes. Noting Thelwall's attention to lower classes, Coleridge claimed that "Thelwall [was] the voice of tens of thousands." For this activity, he was charged with high treason and imprisoned for seven months. During his imprisonment he gained notoriety as a hero. After his confinement he wrote "Poems written in close confinement in the Tower and Newgate." Despite his fame, his personal life suffered. When he visited Coleridge and Wordsworth at their home in Alfoxden in 1797, a spy investigated the visit and consequently the Wordsworths lost their lease. In a letter written in July of 1830, Coleridge recalled a conversation with Thelwall at Alfoxden: "Citizen John Thelwall had something good about him . . . I said to him - 'Citizen John! this is a fine place to talk treason in!' 'Nay! Citizen Samuel!' replied he, 'it is a place to make a man forget that there is any necessity for treason.'" He retreated from public life to a farm in Llys-Wen in Wales where he continued to be harassed and suffered from more personal trials. His daughter's death and a harvest crisis occurring in 1799 encouraged him to move back to London. In 1800 he became a teacher of elocution later publishing "Treatment of Cases of Defective Utterance."

Thelwall's Arthurian drama, The Fairy of the Lake, was published in his book Poems Chiefly Written in Retirement. This dramatic romance is divided into three acts. In the first act Rowenna, the prime antagonist of Arthur's rule, hears of an evil omen about Arthur's reign. She conjures up the Fates, the Furies, and an incubus. She asks the Fates about Arthur's future, hoping that she will have an opportunity to reign. They reply with vague answers which she interprets in her favor. In Act II the incubus helps her to gain power over Arthur by freezing his knights. Rowenna then charms Arthur to sleep. She takes away his sword and when he awakes they argue over his constancy and Guenevere's virtue. Fortunately the knights and the Lady of the Lake interrupt and save him. In Act III Arthur has a banquet. The festivities are interrupted by the death of Vortigern. A dispute occurs between Arthur and Rowenna causing a battle between his court and her group. During this battle Guenevere and Tristram are burned to death. Arthur retaliates by burning Rowenna and her group with the castle. The ruined castle sinks into the moat which becomes a lake. The Lady of the Lake rises and returns Tristram and Guenevere to Arthur. In the end virtue wins.

The first edition of Poems Chiefly Written in Retirement sold two thousand copies and was reviewed by Francis Jeffrey in 1803. In the review Jeffrey mainly quoted sections of Thelwall's prefatory memoir and poetry giving little critical attention to the writing itself. Finally at the end of the review Jeffrey censures his poetry and politics, "middling as his poetry is, however, we shall be happy to find that it affords him a subsistence; because it is a great deal better than his politics."

In 1816 his first wife died and three years later he married Cecil Boyle who later wrote his biography, The Life of John Thelwall. His political interests were renewed in 1818 when he purchased a journal called The Champion which he used as a platform to advocate parliamentary reform. He maintained this interest in politics until his death in 1834.