This is all over the Internet attributed to Winston Churchill (including this website and Quoteland). It is actually:
Great use they have, when in the hands
Of one like me, who understands,
Who understands the time and place,
The person, manner, and the grace,
Which fools neglect; so that we find,
If all the requisites are join'd,
From whence a perfect joke must spring,
A joke's a very serious thing.
~
Charles Churchill, from “The Ghost” (book IV, lines 1379-1387),
1762 http://www.quoteland.com/author.asp?AUTHOR_ID=1480http://www.fullbooks.com/Poetical-Works7.html