Regarding Nick Bowcott, he should never demo amps, he does not have the type of playing/hands to persuade someone to buy a Marshall. Check out his Sweetwater demos...yikes!
It did not mention, for example, how the Marshall 18 watt, model 1974, was eventually rediscovered and led to a huge subculture of amp builders and tweakers. A subculture important enough that it caused Marshall to reissue the amp. And of course Pete Townsend MORE famously used Hiwatts (but I wouldn't expect them to go on about that!)
Of course the Marshall story leaves out the part where they suffered growing pains, much like every
small builder has gone through. That point where a spike in demand made it tough to stay on top of consistency and quality control. One build may be magical, the next a complete dog.
This is why they were pretty much forced to go to the later JCM800 series.
We also know Pete Townshend and Jim Marshall split over endorsement.
My father had few kind words about original Vox and Marshall amps.
He referred to them as similar to working on a beat up old Jaguar XKE
with a faulty Lucas ignition system.
To him, the only British amps worth a damn were the Hiwatts.
My father had the service contract to every major music chain in the area.
I'm certain he ended up working on many failed back line rigs, from the mid-late 60's on.
He employed 10 full time bench techs.
Looking back, I wish I would have talked him into starting his own amp company.