Sycamore,
The K3/K3 trial was an extension of the cleared receiving envelope for the K3. Quite reasonably the TP handled the receiver ac. Just as they have been for a more recent envelope extension of a FJ aeroplane. So why did a DEARer crew have to fly the tanker on the 130J receiver trial in the US.....
The other trial was an equipment trial of the VC10 JTIDS. The DEARer pilot, nav and engineer all agreed that the high level help were the only ones causing difficulties; we knew and agreed precisely who would do what. But I certainly learned that boffins need to be watched - one of them turned off a switch on the Air Engineers panel with the corner of a clumsily handled document....
pi$$ taking apart, if I can be trusted to assess the handling of the aircraft on a full post-maintenance air test which includes taking it beyond the envelope cleared for use by routine sqn operation, I can't really see that a straightforward equipment trial really needs TP expertise. Not their fault, of course - just 'the system'!