I've read a bit about the history of the British bike industry and Edward Turner. I've formed the impression that he was a bit of a dick. His designs mostly needed to be re-designed by others to make them work, and he made dumb management decisions.
Yes this is true , it seems he was not an easy guy to work with , and his attitude to people he worked with was very much in the old fashioned style of a " boss " , he would refer to you by your surname only , but expected to be called Mr Turner in return .
I don`t like to comment normally on people I have never actually met , but this does seem to be the general held view ( and it makes for good story telling , to perpetuate a myth which may or not be true ) .
The re-designing thing you mention is born out by a story of someone studying a component part of a Triumph twin at Meriden , and entering the drawing office to dig out the relevant diagrams for the part .
When he studied the drawings he found they bore little resemblance to the item he was holding and when he queried this he was told " Oh , those are ET`s originals , what you want to look at is these "...and was handed a different set of drawings...the component had been re-designed in order to work properly and new drawings produced to suit .
All this was done without Turners knowledge and if he had found out he would have hit the roof .
He was always right ( of course ) and no one was willing to challenge him , or so it seems .
There was also the story of an industrial engine he insisted on designing , the sort of thing you want to thump along at low revs to pull or lift things....Turners engine was designed as you would a bike engine , with all the power at the top , and promptly stalled when any load was applied to it .
He also wasn`t above tearing into people , balling them out over the most trivial of things .
He had a natural flair for design , understanding the sort of things that a rider looks for in a bike , sprucing up the line up of Triumph singles when he joined the newly formed Triumph Engineering Company in 1936 , which split from the original Triumph Motors , giving these sexed up singles names to match their top speeds , Tiger 70 , 80 and 90 .
He was responsible for the Ariel Square Four calling it " a thoroughly bad design , but people liked it " , displaying an understanding of his own talents that only he was allowed to comment on , re-enforcing his "It`ll be done my way , right or wrong " attitude .
He also designed the 2500 cc V8 engine for the Daimler Dart SP250 sports car ; designer Jack Wickes also worked on that car , Turner once saying " Ah , young Wickes , he`s my pencil ", again demonstrating his attitude towards people who worked under him .
At the same time he was quite prepared to take his bikes out for test runs and cover serious mileage on them , although if he found a bike wasn`t up to scratch he would let the machine fall over on it`s side on his return to the factory , without even bothering to put it on it`s stand .
His main concern was to produce machines in large numbers to sell to as many people as possible to make money for the company , and even when the small car threatened sales in Britain , he fashioned the twins to appeal to the American leisure market , ensuring continued sales and profits , until the late `sixties at least , but he had retired by then anyway .
The fact that a factory in Thailand is still producing motorcycles in 2022 with an engine designed to mimic the appearance of the one he designed back in 1937 would almost certainly be regarded by him as a great compliment , and he`d probably be right .
He visited Japan in the early `sixties and was astounded by what he found there , reporting back to the BSA board his findings , so he understood exactly what the Japanese threat was , but by that time he was close to retirement , and the boards attitude was that our big twins are still selling in the USA , so why worry ( BSA won the Queens Award for Industry for motorcycle exports two years running in the late `sixties , only months before collapse ) , heads firmly buried in the sand , unable or unwilling to face up to what was now just around the corner....