The whole thread gave our friends from that little island in the North Sea, who also happen to drive on the wrong side of the road, a platform to voice their dislike for primary donate. Nice ...
It is not just in UK, as I reported, also here in Italy a number of organisations do not teach primary donate.
Personally I think that there is never just "one right way" of doing the things, there are always several ones.
Primary donate can be effective in some circumstances (definitely in the ones where this method was developed, deep penetration in caves by technical divers, in a very special type of American caves). Then it did proof useful in other environments, such as deep wrecks with multiple gas sources.
These conditions are very different from rec diving in resorts or in guided groups, where most divers are beginners, and simple, standardised procedures and equipment are more easily taught.
So, as I have nothing against those special procedures to be employed in those high-tech environments, please understand and accept that millions of divers all around the world were not trained for primary donate, they are not equipped with a primary very long hose routed under the arms and around the neck (a configuration which requires some manoeuvre for freeing the hose when donating). They are taught to always keep well visible a yellow octo with a longer than normal, but not so long, yellow hose, and that this device is the alternate air source both for them and for their buddy.
When approximately 30 years ago the usage of a secondary rec (at that time it was not an octo, it was a completely independent reg with his own first stage and valve) became standard, and we finally did not need anymore to "buddy breath" from a single reg, this configuration was standardised among substantially all the training agencies worldwide.
Problems started to arise when a significant number of non-technical divers started to employ those DIR-GUE methods outside the context for which they were developed, and assumed it was fine to dive in touristic sites together with "normal" (non tech) recreational divers, which are trained and used to different methods.
The danger comes from the mixture of different approaches, and negates one fundamental point of the Hogarthian-DIR philosophy: very strict standardisation of procedures, methods and equipment.
Also at the time I was working as a professional instructor, sometimes some customer did arrive at the resort with out-of-standard equipment: one of the first, very dangerous dry suits, a single double hose reg with no backup, or a reg without SPG. There was even people not wanting to use a BCD...
Apart some noticeable exceptions, we did never allow those guys to employ their not standard equipment or procedures.
Please understand my position: I was responsible for the safety of our customers, and so I had the right and the power to enforce the safety procedures which my organization had standardised. Customers had the choice to comply, or not to dive. It is simple.
And now with Coronavirus it is the same: a "safety" procedure is mandated, and if you do not want to comply, then you are refused diving. If you think that the procedure can be improved, resulting in better safety, you must convince the regulating body to change the procedure for everyone, You cannot say "hey, but this does not apply to me" and dive without respect for the mandatory procedures.
It appears that GUE did understand this very well, and has adapted equipment and procedures for complying. All other training agencies are doing the same. When conditions change, everything must be adapted accordingly, and you cannot expect to be able to keep the same as before the conditions changed.