Grease and line your loaf tin and set the oven to 170ºc / gas mark 3
Melt the butter and sugar in a pan, over a medium heat
Remove from the heat and mix in the bananas
Add the egg and mix well
Stir in the flour and milk
Pour into your tin and sprinkle over the demerara sugar
Place in the middle of the oven for 45 minutes (or until a skewer or knife comes out clean) and leave to cool a little, if you can resist!