He was appointed as a Knight of the Order of Charles III by Isabella II, Queen of Spain in 1838, and was knighted and granted permission to use his Spanish knighthood in Britain.[3] He was also a Knight Commander of the Military Order of St Ferdinand.
In 1847 he reluctantly accepted the governorship of Newfoundland.[2] Le Marchant was opposed to the idea of responsible government and condemned local merchants of amassing wealth in the Colony and then returning to England. After the fire of 1846 funds were collected for the victims and Le Marchant, acting upon Robert Law's recommendation that no further money be given to victims, then directed funds to the repair of public buildings and construction of roads in St. John's and the outports.[2]
Note: The year after Sir John Harvey had stepped down as governor of Newfoundland, and until Sir John LeMarchant was appointed, the colony was administered by Robert Law, a British army officer.