A private swimming-pool

During the war a swimming-pool was built behind me British positions. It was reserved for officers only. An old sergeant major was to look after it.
Soon the Tommies got to know of the swimming-pool and began using it.

The colonel sent for the sergeant major and asked him:
"Do you know that the Tommies use the swimming-pool?"
"Yes sir," the sergeant major replied.
"Then, how is that? Didn't I tell you to keep the pool reserved for officers?" asked the colonel.
"Yes, sir," repeated the sergeant major.
"Then why do you let the Tommies use it?" asked the colonel angrily.
"Well, sir, it's like this, how do I know a private from an officer when they all run down naked?" — said the poor sergeant major.