Throughout his campaign to be President Donald Trump promised to build a wall between the United States and Mexico. Upon taking office he vowed to keep the promise. Someone who knows from personal experience what it's like to patrol that southern border is Mark Napier, who is the Sheriff of Pima County in Arizona. As he explained to Eddie Mair one of the biggest challenges he and his team face is the topography of the area and the very hot climate. "Every year 150 bodies are recovered in the desert of people who have tried to come across the border, but have died because of the environmental conditions".