A couple of things to throw into the fray.
Having been streamed to Gp1, my first tour having never failed anything, was on the Puma in 82! I did 2 tours, the second as the Sqn Trg Officer, both with single pilot ops as normal. This, considering how poor the nav kit was at the time and the heights we flew at, was hard work. Consequently the crewmen (of multiple backgrounds) gave excellent help in the front when not need in the rear. As CG stated two pilot ops started to come in as the norm about the Gulf War time and for NI ops. NVG was coming in big time in the late 80’s and was proving to be an issue on manpower as was proved in the Gulf War. The Sqn in RAFG had 17 a/c and 17 pilots….. Indeed, on some exercises I recall being ferried back to base to pick up another frame as we had more of them than crew and on one occasion flew completely solo; it was allowed then.
Anyway, on to NVG. Yes, this needed 2 in the front. In the late 80’s I completed a conversion and started the slow process of getting others up to speed. As part of this it was intended to use the Navs in the LHS. Consequently, I was tasked with getting them up to speed to fly the aircraft if needed so yes some non pilots were given training. However, there was sometimes a reason why they were navs, not pilots!
Events overtook this and the Gulf War arrived and the trawl went out for Puma pilots, or anyone that had seen one and the most current ended up in the ME. It was then the job of a couple of us to get all trained up for NVG. 90 mins for the RHS, 60 for the left. Not a single incident and the Puma force became NVG capable and the end of single pilot ops dawned.
In the way of the RAF, I then headed off to pastures new and a Flt Cdr tour on the C130K. Here, unless you were on SF(!), it was 2 pilot ops. A grand time was had in the TAC role in a great multi crew environment. However, in answer to the question above, even practice double asymmetric flying was not easy. The outer engines on the C130 are a long way out from the centreline and they were at full power at times. Flying was all manual and it was impossible to trim out the rudder forces and there was subsequent aileron deflection. Basically, the captain flew, the rest of the crew operated. I am aware that modern aircraft are different having flown the A321/330.
So, in summary, whilst single pilot ops are and were for many years, possible but on some occasions, particularly on angry ops, not a good idea.
To further explore some more parts of the thread. Gp3 was called that because it came after fighters and transport a/c and was therefore logical. It was not for the also rans. One of my fellow streamed Gp3 colleagues was replaced by a medically downgraded student and he went to lightnings and several I knew transitioned to Hawk instructor, Buccaneer and Harrier. In all forms of flying I have done, I have met some excellent pilots and crew and as said above, we are all on the same team.
Me