Computing: The German Democratic Republic bequeathed a 600m-piece puzzle to the reunified country. It is about to be solved using software.

WHEN the shredding machines failed and the mob was at the gates, the spooks at East Germany's State Security Service, better known as the Stasi, tried turning their files into mush by dunking them in water. But the number of bathtubs in their headquarters in Normannenstrasse was as unequal to the task as the machines had been. In the end, they resorted to tearing each page up by hand. The fact that many of the resulting shreds are only a few millimetres across is testament to just how much the soon-to-be-ex-members of the intelligence service did not want their work to fall into the public domain.