Based on those figures, every tonne you carry for 25 hours burns ---- a tonne to carry it.
Casting my admittedly crumbling memory back to Lightning days I'm sure that when in over wing tank fit they used to take off with the tanks empty and then fill them at the tanker. I think if they took off with full overwing tanks they arrived at the tanker with less fuel on board than if they took off with them empty...