He was born in Dublin on 17 January 1756. Walks along the North Wall of the Liffey developed his urge to travel, and in 1773 he joined the army, enlisting in the 9th Foot. In 1776 he was posted to America, serving under Burgoyne, Clinton and Cornwallis. Captured at Saratoga in 1777 and later in North Carolina, he made two escapes, the second with four others by digging a tunnel under the wall of Philadelphia Gaol. Returning to England he was discharged at Winchester, but refused a pension as his service was less than 20 years. He then returned to Dublin where he heard John Wesley preach and became a Methodist, married a widow with several children, and became a schoolmaster. In 1793 he was appointed the master of the free school at Whitefriar Street which prospered and grew under his mastership. He exercised a great and good influence on the boys he taught. He was a member of the Strangers' Friend Society. He published a book about his American experiences and another about his own life. He died in Dublin on 28 January 1830.
He was married at least twice: on 15 January 1786, four months before his conversion on 26 May, to Jane Crumner, a widow with previous children.; and in 1805 to Ann Young(e) (1767-1823).
Robert Graves used Lamb's military experience as a basis for a number of his books, such as Sergeant Lamb of the North (1940)and Proceed, Sergeant Lamb" (1941).