1. Preheat the oven to 190c.
2. Grease and line a 12x7 inch shallow baking tin.
3. Put the butter, Caster Sugar and Golden Syrup in a pan and place over a medium heat, stirring until melted.
4. Take the pan off the heat, add the Quaker Oats, walnuts and orange zest and mix well.
5. Tip the mixture into the baking tin and spread evenly.
6. Place in the pre-heated oven and bake for about 30 minutes until golden brown (but with the centre still soft).
7. Remove from the oven and mark into 12 rectangles whilst still warm, then allow to cool for 5 minutes.
8. Heat the orange marmalade with the tbsp of water. When melted, brush the marmalade glaze onto the flapjacks and let them go cold in the tin before cutting into the marked rectangles.