Was there really a USn judge called Learned Hand? Or was that just a pen name, and if it was, what was his/her real name?

There most certainly was, bingley: "one of the great judges of the twentieth century, whose work has left a profound mark on our legal, intellectual, and social landscape. ... Learned Hand is widely considered the peer of Justices Holmes, Brandeis, and Cardozo." And thank you, bingley, for prompting me to do a bit of research; I am now eagerly running off to purchase the biography. A few quick quotations of Justice Hand:

"If we are to keep our democracy, there must be one commandment: Thou shalt not ration justice. (1951)

The spirit of liberty is the spirit which is not too sure that it is right; the spirit of liberty is the spirit which seeks to understand the minds of other men and women; the spirit of liberty is the spirit which weighs their interests alongside its own without bias; the spirit of liberty remembers that not even a sparrow falls to earth unheeded; the spirit of liberty is the spirit of Him who, near two thousand years ago, taught mankind that lesson it has never learned, but has never quite forgotten; that there may be a kingdom where the least shall be heard and considered side by side with the greatest." p. 190-191, The Spirit of Liberty (1944).