Heat oven to 200C/180C fan/gas 6.
Whizz the porridge oats and butter
together in a food processor, or rub the
butter into the oats with your fingertips
in a big bowl. Stir in the flours, caster
sugar, bicarb, mixed spice, 1 tsp salt, the
raisins, sultanas, dates and mixed peel.