AtoBsafely FEHoppy
Look up
Linktrained PPrune "Fuel not used"
Sorry not able to give a better reference.
The aircraft was a twin engined biplane ( ! ) and with own my lack of experience, I was reluctant to shut down my Port engine. I was required to fly at 3000 ft for the task, which I did.
Before it got dark, I had not been able to see that the Port exhaust was glowing (or not !). So the first hour was flown using both engines.
After returning to Liverpool The G/Es wanted to know why I had only refuelled one side. ( I hadn't !)
No performance information was available to me, anyway !