Preheat the oven to gas, 180°C, fan 160°C. Grease and line a 2lb loaf tin. Sift the flour into a bowl, then add the milk, vanilla, sugar and eggs. Beat with an electric mixer for up to 1 minute, or until the ingredients are combined and lighter in colour. Pour in the melted butter, then add the mashed banana and beat for a further minute or until well combined. Pour into the tin and bake in the oven for 1 hour 10 minutes. Test to see if it's cooked by inserting a skewer. If it comes out clean, then it's done. If not, give it a few more minutes and check again. Once cooked, remove from the oven and allow to cool in the tin for 5 minutes. Then tip out onto a wire cooling rack and allow to cool completely. If you prefer an iced cake, make up some cream cheese icing and drizzle over before serving. Tip: you can also serve this cake warm straight out of the oven with ice-cream as a pudding. Drizzle with honey or maple syrup for a little added sweetness.