Did a Google search on the terms "Gelhaar U45" and came up with an excerpt from the book "The Gathering Storm: The Naval War in Northern Europe ...". Front Page here:
http://books.google.com/books?id=v8A...page&q&f=false
The tale is told on pages 185-186 - excerpt here:
http://books.google.com/books?id=v8A...%20U45&f=false
My Goggle-fu is fairly good, after lo these many moons of research!