No pic, sorry. The issue was on the inside of the fork, beside the brake rotor, so very difficult to see, never mind take a picture!
I did very carefully scrape the 6 or 7 hard growths or pitting down, and then polish with some chrome polish, im actually thinking now it could be some hard road dirt, or brake debris flicked up by the brake rotor?
I will keep an eye next time I clean the bike.