Preheat the oven to 180C (170C if fan assisted) and grease and line a 1lb loaf tin. Mash the bananas well and set to one side.
Sieve the flour, bicarbonate of soda and salt together in a separate bowl and set aside
In another bowl, cream together the butter/magarine and caster sugar until light, pale and fluffy.
Add in the eggs and vanilla and mix well.
Next, add the mashed bananas and buttermilk.
Finally add in the flour until combined.
Pour the mixture in the prepared tin and cook for around one hour or when a knife inserted comes out clean. If you find your loaf cake is browning too much on top you can drop the oven temperature by 10C or place a piece of foil gently over the top.
Once cooked, leave in the tin to cool for ten minutes before turning out the loaf cake onto a rack and allow to cool completely. Serve on its own or toasted and spread with a knob of butter.