  Roy P. Kerr has discovered his celebrated metric 45 years ago, yet the
problem to find a generalization of the Schwarzschild metric for a rotating
mass was faced much earlier. Lense and Thirring, Bach, Andress, Akeley, Lewis,
van Stockum and others have tried to solve it or to find an approximative
solution at least. In particular Achilles Papapetrou, from 1952 to 1961 in
Berlin, was interested in an exact solution. He directed the author in the late
autumn of 1959 to work on the problem. Why did these pre-Kerr attempts fail?
Comments based on personal reminiscences and old notes.
