
After the war, Durnford became chief engineer and surveyor general of the new colony of West Florida thanks to the patronage of Lord Harcourt. In addition to his modest annual salary, Durnford also earned money for every 100 acres he or his assistants surveyed, which greatly enhanced his income, as land grants of thousands of acres were commonplace in West Florida. Durnford's personal holdings totaled 52,662 acres, the jewel of which was his 5,000-acre plantation, Belle Fontaine, set on the cliffs above Mobile Bay's eastern shore. Located near present-day Montrose, the area was free from the fevers and crowding that plagued Mobile and was also home to Crofton, a military convalescent hospital. As chief engineer, Durnford drew detailed plans for rebuilding the port there, but they were never implemented. He had more success in designing a road, which was partially built, linking Mobile and the colony's capital, Pensacola.

When the American Revolution broke out, Durnford's duties became increasingly military in orientation. In 1779, his military role became even more prominent when Spain entered the fray as an ally of France (which was allied with the Americans), thus joining the seemingly endless wars with Great Britain over colonial territories in the Americas. In January 1780, Durnford took command of Mobile's Fort Charlotte, a crumbling brick edifice built by the French as Fort Condé. On February 10, a sizable Spanish force anchored in Mobile Bay.
Durnford's garrison, a motley collection of sailors, resident volunteers, armed slaves, and regular troops totaled 287. Francisco Bouligny, emissary from the Spanish camp of 2,000 men, met with Durnford and demanded his surrender, which he fully expected to receive given the imbalance of forces. Durnford, however, was awaiting a relief force from British Pensacola and refused. An exchange of wine and cigars between the enemy commanders accompanied continued polite negotiations, even as the Spanish dug trenches and sited siege cannons.

Gálvez completed his conquest of West Florida in 1781 by taking Pensacola. Durnford returned to Britain with his family but resumed his military career in the 1790s, taking part in campaigns against the French in Martinique, Guadaloupe, and St. Lucia. Durnford died in Tobago from yellow fever on June 21, 1794.
Additional Resources
Fabel, Robin F.A. The Economy of British West Florida, 1763-1783. Tuscaloosa: University of Alabama Press, 1988.
Additional Resources
Fabel, Robin F.A. The Economy of British West Florida, 1763-1783. Tuscaloosa: University of Alabama Press, 1988.
Hamilton, Peter J. Colonial Mobile. 1910. Reprint, Tuscaloosa: University of Alabama Press, 1976.
Howard, Clinton N. The British Development of West Florida, 1763-1769. Berkeley: University of California Press, 1947.
Johnson, Cecil. British West Florida, 1763-1783. New Haven, Conn.: Yale University Press, 1942.
Starr, J. Barton. Tories, Dons, and Rebels: The American Revolution in British West Florida. Gainesville: University Presses of Florida, 1976.