When the VC10K fleet first started, all the captains were either ex-Victor/Vulcan AAR or ex-VC10. Some were both. The first co-pilots came from a variety of backgrounds, although it was a couple of years before the first ab-initios arrived. The synergy of this mix led to a sound operational method being evolved, without a legacy of "We always did it this way on the...." dominating. The A330MRTT fleet will probably adopt a similar strategy.
Weren't the VC10 C1 pilots all Sqn Ldrs as well to stop them defecting to the darkside where the pay was greater for those under Sqn Ldr rank, and that only ceased when the Civilian world got rid of them and sold them to the RAF, then you started getting lower ranks flying them.
I wonder if this will happen again with the A330, as a young RAF pilot converted onto type with a few hours under his belt must look a good bet on the civilian airline fleets if things ever pick up.