Police hit the jackpot when they searched an alleged burglar and found a camera.
They processed the film and discovered dozens of pictures of graffiti tags on bus shelters, railway bridges and buildings in Sussex.
The 17-year-old youth was being questioned about the vandalism yesterday.
He was stopped by police in Littlehampton and arrested on suspicion of going equipped to steal.
Officers discovered a screwdriver and a pair of gloves.
They found the camera and decided to have the film processed.
Inspector Julie Wakeford, of Brighton police, said: "We were amazed. The pictures were all of graffiti daubings with the tag 'TOPA'.
"We suspect whoever took the pictures was responsible. We are questioning the youth about them."
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