As a Loyalist, Martin maintained a low profile following the outbreak of the American Revolutionary War. By 1778, the Virginia General Assembly had abolished quit-rents, but in recognition of Lord Fairfax's loyalty, the Northern Neck Proprietary was made an exception. Lord Fairfax was treated with respect and consideration by the assembly, and despite being the only resident peer in the American colonies, he was accorded all the privileges of a Virginia citizen. Following the death of Lord Fairfax in 1781, his will was recorded on March 5, 1782, and conveyed his title to the remnants of his American properties, including the Northern Neck Proprietary, to Martin's elder brother Reverend Denny Martin, who then assumed the surname and coat of arms of Fairfax. Lord Fairfax devised his property and title to Denny Martin on the condition that he apply to the Parliament of Great Britain for an act to authorize him to inherit the title of Lord Fairfax of Cameron. Martin was appointed by his uncle, along with Gabriel Jones and Peter Hog, as an executor of his will and estate. Martin inherited the plantation Lord Fairfax had purchased from John Borden consisting of . Martin was also bequeathed the Greenway Court estate and "all the stock of cattle, sheep, hogs, implements of husbandry, household goods and furniture" there. Martin and his brothers Denny and Philip also inherited all Lord Fairfax's slaves. Martin's uncle and Lord Fairfax's brother Robert Fairfax appealed his claim to the title of Lord Fairfax of Cameron to Parliament, and succeeded as the 7th Lord Fairfax of Cameron.