Bicycle Tag of bike

Do I Brain Stew's visual clues explain that protusion on the PC's head ?
Anyway I'm no closer to pinpointing the tag.
Perhaps I shouldn't occupy more page space with my inconclusions.

A custodian would probably be prudent (if ineffectual) - although I'd have thought that is all in the past by now.

Another clue to put some pressure on those who know, but haven't turned the pedals to tag:
An alternative name for those guys who sang "Two Princes"