[1][2] Upon arriving in North Africa to take up the post, Teviot implemented major reforms to the Tangier Garrison during his tenure in office.

Teviot also ordered the construction of several outlying fortifications to protect Tangier and won several victories over the forces of Khadir Ghaïlan (known to the English as "Guyland"), a local Moroccan warlord.

Some historical accounts suggest that Teviot had made plans to gather stocks of stone, timber and other building materials from the surrounding areas, though other accounts suggested that Teviot's expedition may have been intended to forage the local area or that he planned to cut down a patch of brushwood that Moroccan forces had used as cover during their previous attacks on Tangier.

They pursued the fleeing enemy, but it quickly became apparent that this was a trap as a much larger Moroccan force of 8,000 men under the command of Ghaïlan was waiting to ambush them.

Following Teviot's death, the position of governor and command over the Tangier Garrison devolved to his Irish subordinate, John Fitzgerald.