Mitchell-Hedges spent some years alternating between Central America, the Caribbean, the United Kingdom, and the United States. Some sources say he was a mercenary, others that he was a British government spy, and others that he was independently wealthy and traveling for diversion. Some of his "expeditions" to Central America were financed by well-to-do British socialites. He was also supported by the British Museum to whom he donated numerous artifacts.
Mitchell-Hedges repeatedly made claims of having "discovered" Indian tribes and "lost cities" that had already been documented years, sometimes centuries, before. He claimed he discovered "the cradle of civilization" in the Mosquito Coast of Nicaragua, and that the Bay Islands of Honduras were remnants of the lost civilization of Atlantis.
In 1906 he married Lillian Agnes Clarke, known as "Dolly". Most of the time he lived apart from his wife. They had no children on their own but adopted Canadian orphan Anne Marie Le Guillon, today known as Anna Mitchell-Hedges.
For a time in the 1930s he had a weekly radio show out of New York City on Sunday evenings. Talking over a background of "jungle drums", Mitchell-Hedges would tell dramatic tales of his adventures, usually including narrow escapes from death at the hands of "savages" or from jungle animals ranging from a jaguar to a vicious attacking iguana.
Mitchell-Hedges claimed to have discovered a "crystal skull" — he called it "The Skull of Doom" — at the Maya ruin of Lubaantun, which he also claimed to have discovered in British Honduras in the 1920s. However he published no mention of the skull until the late 1940s, not long after a crystal skull was auctioned off at Sotheby's in 1943. Some think that Mitchell-Hedges' crystal skull is actually the one from Sotheby's. He died in June of 1959.