Preheat oven to 180 degrees C. Grease and flour two 23cm round cake tins.
Combine flour, oats, bicarbonate of soda, baking powder and salt in a medium size bowl.
In a large bowl cream the butter. Add brown sugar, sugar, allspice and nutmeg; beat until light and fluffy. Mix in eggs and vanilla essence.
Add 1/3 of the dry ingredients to the butter mixture; mix well. Add the sour cream; mix well. Add another 1/3 of the dry ingredients; mix well. Add half of the bananas; mix well. Repeat with remaining 1/3 of the dry ingredients and remaining bananas. Pour batter into prepared tins.
Bake until cake tests done; about 30 minutes. Let it cool in the pan for 5 minutes and then turn onto wire rack to cool. Frost with you favourite icing.