Ever since he was a boy, Horst Müller has dreamt of finding a fabled steam engine lost in the waters of the Rhine. He combed municipal archives, read every record he could get his hands on, raised tens of thousands of euros and called in a geophysicist from the other end of Germany.

Then, in one wonderful moment, Mr Müller, now 68 and retired from his job as a train driver, thought he had found it, lying in silt, gravel and murky water. But a colossal civil engineering effort that turned over more than 450 sq m of riverbed to a depth of 9m has come up with nothing. “I’m baffled and bewildered,” Bernhard Forkmann, the geophysicist, said. “I cannot explain to myself what