To the dustmen of Frankfurt, they were a mess that needed to be cleared from the streets of their spotless city. The yellow plastic sheets were swiftly scooped up, crushed and burned. But the diligence of the rubbish collectors was little consolation to the city’s prestigious art academy, which is now ruing the loss of an important work.

To those who knew him in the sleepy German village, he was a nice, shy young fellow who spent too long on his computer in his bedroom at home. For 18-million computer users, though, Sven Jaschan was not your average introverted teenager, but the author of an internet virus called Sasser that caused havoc from Britain to Australia and untold financial harm to businesses in between.