If you look on the side of the 125’s fairing you’ll see “YCE” this is York Chisnall Engineering.The reason I mentioned it is that I'm sure I remember the 125 being entered as a "Broad Yamaha."
Every Broad owned or sponsored bike I’ve ever seen has “Broad Yamaha” on it, there’s no markings like this on John’s bike. I have another 8 period photos and no mention of Broad. Who knows, I’ll ask Ted’s son.
john Chisnall is still about although not so active nowadays.