The Diary of a U-boat Commander

The Diary of a U-boat Commander is a classic and fascinating World War One history text about the life of a German U-boat commander and a gripping war biography.
This venerable WW1 history text contains the following exerpt:
"I would ask you a favour," said the German captain, as we sat in the cabin of a U-boat which had just been added to the long line of bedraggled captives which stretched themselves for a mile or more in Harwich Harbour, in November, 1918.
I made no reply; I had just granted him a favour by allowing him to leave the upper deck of the submarine, in order that he might await the motor launch in some sort of privacy; why should he ask for more?
Undeterred by my silence, he continued: "I have a great friend, Lieutenant-zu-See Von Schenk, who brought U.122 over last week; he has lost a diary, quite private, he left it in error; can he have it?"
I deliberated, felt a certain pity, then remembered the Belgian Prince and other things, and so, looking the German in the face, I said:
"I can do nothing."