Who made Energen Rolls, and what actually were they?

Energen was the brand name for a bread roll that was supposed to be useful as a diet aid when eaten instead of regular bread. At least, that is how they were advertised in the 1930s. They seem to be high protein and low starch.
https://www.google.com.au/search?q=energen+rolls&client=firefox-b&dcr=0&tbm=isch&source=iu&ictx=1&fir=LToitwm1rYiqsM%253A%252CtNwSzBibJLebPM%252C_&usg=__oye8ZabgLBbHWRKosnCTz3nTU0k%3D&sa=X&ved=0ahUKEwi4hobXm6naAhVLi7wKHaLBAnwQ9QEIKTAA#imgrc=IV6TYitw7DV0eM:

I find most people who remember them now from their childhood (they were discontinued in the 1970s) describing them as crunchy, and delicious when eaten with plenty of butter, so probably not a great diet food when consumed that way!

https://www.doyouremember.co.uk/memory/energen-rolls

I remember them. I expect my mother bought them as my abiding memory is that she would try anything suggested as a way of losing weight.They were supposed to be a substitute for bread, but they had a very crisp outside and absolutely nothing inside except air, so there was little substance to them.

https://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/energen-rolls

As I remember (from my mother's dieting after she stopped going for walks and started playing bridge...), they had something inside that was dead white and rather wispy. She went on to Ryvita, which is still going. I've seen them described as all the gluten with almost all the starch taken away, but I've not seen anything about who made the things. I'm surprised they haven't got an article on Wikipedia, as they did attract quite a bit of discussion.

They were made by the Energen Foods Company in London.
https://www.gracesguide.co.uk/Energen_Foods_Co