Who would have guessed that it wasn't just someone's grandmother's recipe? I've eaten a fair number of those pickled onions, as they are always served with the classic ploughman's lunch, in every pub in Great Britain.
One item in the video that caught my attention was that so many of the onions came from Egypt. The reason that struck me is that, back in the day when Egyptians mummified their royalty, they used onions to replace eyeballs. So they've had a lot of experience getting onions to just about the exact size shown in the video.