[2][3] Born at Latchford on 9 June 1762, he was the eldest son of John Drinkwater (1740–1797), a surgeon in the Royal Navy,[4] and his first wife Elizabeth Andrews.

At the age of fifteen he joined the 72nd Regiment of Foot (Royal Manchester Volunteers) as an ensign and was almost immediately posted to Gibraltar.

[5] From June 1779 to February 1783 this small British possession was under siege from French and Spanish forces, during which time he kept a careful record of events.

From his notes he wrote A history of the late siege of Gibraltar, 1779–1783, with a description and account of that garrison from the earliest period, published in 1785, which was widely read and frequently reprinted.

From there, he served under the viceroy, Sir Gilbert Eliott, as military secretary and deputy judge-advocate of the Kingdom of Corsica until the French captured the island in October 1796.

Under Captain George Cockburn, it carried the flag of Commodore Horatio Nelson, whom Drinkwater had made friends with in Corsica.

In 1799 he married, and was also appointed commissary general of the British forces in the Anglo-Russian invasion of Holland, where he served until evacuation in November 1799.

His experience there led to the offer of a ministerial post in 1807, to serve under William Windham as Under-Secretary of State for War and the Colonies, but he declined.