UK suffered from the import of better quality faster and better handling bikes from Japan and the UK bike manufacturers were too slow to even attempt to play catch up.
I agree, it was a shame because they had serious warnings. When the 305 Honda motor came out they should have taken note. But 1969 with the 750 Four it was over for them.
Old man Honda didn't keep it a secret. They intended to make fast, reliable and affordable bikes. They did. Harley and the British sat on their logos doing nothing to compete.
We make fun of AMF but had they not been involved for a decade the Harley name would just be in the history books. They made the HD branding and logo wear a big business. So who needs engineering to go with it.