He was educated by Adam Hill, prebendary and succentor of Salisbury Cathedral, proceeding about 1572 to Balliol College, Oxford, where he studied for two years as a fellow commoner.
Along with an Italian guide, a serving man and a page, provided by his father, he crossed to France towards the close of 1574, visited the court of Henri III, and procured letters of commendation to the emperor, Maximilian II.
Vennar went to prison at least twice during the affair, for allegedly stealing documents and for debt; he thought his reputation had been destroyed, and was determined to rehabilitate himself.
His good reception aroused Queen Elizabeth's anger, and on his return to England he was promptly arrested and imprisoned for a short time "as a dangerous member to the state".
In 1614 he wrote a vehement protest, entitled An Apology: written by Richard Vennar of Lincolnes Inne, abusively called Englands Joy.
The work is divided into two parts, of which the first is autobiographical, and the second relates Vennar's exertions to obtain the abolition of imprisonment for debt in England.
[2] Several allusions to "England's Joy" occur in contemporary literature, particularly in Ben Jonson's Love Restored (1610–11), in his The Masque of Augurs (1622), and in Sir John Suckling's comedy The Goblins (1646).
A poem entitled "Englands Joy", R. R., published without date, place, or printer's name, is sometimes attributed to exiled Recusant Richard Verstegan, but was believed by Louise Guiney to be the work of John Vennar.
William Fennor wrote that Vennar had objected to fees demanded in the compter and been thrown into the black hole, where "lying without a bedde, hee caught such an extreame cold in his legges, that it was not long before he departed this life".