Put the raisins in a small saucepan over a low heat with the orange juice and bring to a gentle simmer. Remove from the heat but leave in a warm place for the raisins to plump up with the orange juice.
In another larger pan place the butter, golden syrup, orange zest, brown sugar, lemon juice and rum. Heat gently, stirring occasionally until the butter has melted and the sugar has dissolved.
Mix together the oats, flour and toasted pine nuts in a large mixing basin. Pour in the melted butter mixture and the raisins, along with any juice left in the pan. Mix everything very thoroughly, being careful to incorporate all the dry ingredients from the bottom and edges of the mixing bowl.
When thoroughly mixed, spread the mixture out in a greased, lined tin and bake in a moderate oven 160C/325F/Gas 3 for 25-30 minutes until golden brown.
Cut into squares with a knife while still warm and soft, then leave to cool and set.