In a small bowl, combine the mayonnaise and basil. Set aside.
Place the bread under the broiler and toast until golden brown, Flip the bread slices over and continue to toast until golden.
Transfer the bread to a platter or plate and spread the basil mayonnaise liberally on one side of each slice being sure to cover the entire surface. Layer two slices of bread with peaches and top each with 1/2 cup arugula. Top the arugula with the bacon and the remaining slice of bread. But the sandwich on an angle, corner to corner and serve immediately.