Damian Drooth, Supersleuth: Football Forgery by Barbara Mitchelhill
Damian Drooth, ace detective, stumbles on a new case at the local football ground. Someone is selling forged tickets and it's up to our hero to find the culprit. After several false starts, the only evidence is a photo taken by a classmate - a girl! Damian realises it's vital to get that photo if he is to solve the crime. This is the ninth book in the series.