Possible Clues:

• Outdated
• Russian river fish -- by the smell, going out of date
• Going out of use
• Only perfume used by ex-pupil on the way out
• Celebs not so new, on the way out
• Ageing old boy's unique smell
• Old boy's pocketing single coin that's almost out of date
• Celeb's not so fashionable — could be past it
• Bad smell rising - fish smell - past its sell-by date?
• Ageing old boy with unique odour