I've never even heard of a Nazi slave ship. But the book is cool
Yet another dramatic chapter in the history of the British Navy was written when on February 16 H.M.S. "Cossack" pursued the Nazi slave-ship "Altmark" into a Norwegian fjord and rescued 299 British prisoners at the point of the bayonet. Below is a recapitulation of the episode based on Admiralty statements and eye-witness stories.
The slave ship was almost home. Two months and more had passed since she parted company from the "Admiral Graf Spee" after receiving from the pocket battleship her last captures of British prisoners. That was on December 6, somewhere in the South Atlantic, and since then while the "Graf Spee" was resting and sinking ever deeper into the Montevidean sandbank, the "Altmark" had ploughed a zigzag course heading northward. She reached at last the cold waters of Iceland, and now turned south past the towering cliffs of Norway. On February 14 she got into Norwegian territorial waters of Trondheim Fjord and (according to the Norwegian Prime Minister) was stopped and "examined" by a Norwegian torpedo boat. She was allowed to continue her journey, but next day, 100 miles north of Bergen, was again stopped by a Norwegian warship, and refused a request that she should be searched. The afternoon of Friday, February 16, found her approaching Norway's southernmost point; a very short distance beyond lay the Skagerrak, safety, and home...
HMS Cossack and crew which liberated the British prisoners.