Heat the grill until very hot. Cut eight slices of the bread about a half inch thick and on the diagonal. Drizzle one side with some olive oil. Place on the grill and toast for about two minutes each side. Don't leave them as they burn very quickly! Once they're toasted, leave to the side and make the avocado. Place the avocados in a bowl and mash with a fork. Add the lemon juice, garlic, basil, salt and pepper. Stir gently to combine. Spoon onto each bruschetta slice. Drizzle some more olive oil over the avocado and serve at once.