Preheat the oven to 200C/400F/Gas 6. Grease and line two medium (or three small) loaf tins.
Mash the bananas and vegetable oil together in a bowl and set aside.
In a separate mixing bowl, cream the butter and sugar together until pale and fluffy. Beat in the eggs, one at a time, then stir in the mashed banana mixture until well combined.
Mix the flour, baking powder, ground spices and salt together in another bowl and lightly fold into the banana mixture. Add the raisins and pecans and fold together lightly.
Spoon the cake mixture into the loaf tins and bake in the oven for 1½ hours, or until risen and golden-brown. Check after one hour and reduce the oven temperature slightly if the loaves are browning too quickly on the top, or cover the loaves loosely with aluminium foil.
Leave the banana bread to cool in the tins, then turn out and serve in thick slices.