Back in my ‘yoof’ when I worked for the same firm as Lofty Avis I recall that he had the front half of his pipes given some kind of “alumised” treatment, (sprayed on?). It resulted in a matt white finish that looked tidy, was cheaper than a re-chrome job and stayed on well. I don’t recall it being affected by exhaust heat but was prey to discolouration from road dirt and had to be repeated from time to time for appearances sake.
Now all that was the best part of 40 years ago and my memory ‘aint wot it used to be, (in truth it never was), also being quite senior in the Company he had a fine contempt for all apprentices and ‘specially for one riding a Vincent! Furthermore, back then, greasy ‘orrible apprentice oiks only spoke to the bosses when spoken to, as a result I never got much information but maybe someone else knows/recalls more about the process?