Preheat the oven to 325 degrees. Butter a loaf pan.
Sift the flour, baking soda and salt into a medium bowl; stir in the walnuts, set aside. Whisk the eggs and vanilla together.
In a mixing bown cream the butter and sugar until light and fluffy. Gradually pour the egg mixture into the butter while mixing until incorporated.
In a small bowl, mash the bananas with a fork. Mix in the milk and cinnamon.
Add the banana mixture to the creamed mixture and stir until combined. Add dry ingredients, mixing just until flour disappears.
Pour batter into prepared pan and bake 1 hour to 1 hour and 10 minutes, until a toothpick inserted in the center comes out clean. Set aside to cool on a rack for 15 minutes. Remove bread from pan, invert onto rack and cool completely before slicing.