About the only thing interesting or challenging about AT flying in the VC10 was the art of fuel calculation, so that the Air Movs people could have the best possible payload offered.
Nowadays a good mission planning system can plan the minimum fuel load required for even a very complex AAR trail mission to the last kilogram in a few seconds. Either statistical, still-air or forecast met data can be used and due allowance made for contingency fuel requirements. Play tunes on prudent extra fuel requirements and payload and a good AT/AAR solution can be found, essential for a multi-role tanker transport aircraft.
A pity that some air forces still have to rely on last century planning methods though.... They must waste thousands of kilograms burning fuel to carry unnecessary extra fuel due to excessively conservative fuel planning.
I once did a transit back from Goose to the UK with a very good tailwind in a VC10K2 with a high ZFW. The very experienced navigator computed the fuel and I rounded it up a little further for a little 'wotif' comfort.. But an old Victor captain travelling in the back advised me to 'fill it up' - because that's what they always did on Victors. The Nav and I both told him he was wrong; had we followed his 'advice' we'd probably have been over max normal landing weight back at Brize....