Bjorn,
Check the "Boston Evening Transcript" November 26, 1872 for a letter by
Clemens...but easier than that see: "British Benevolence" in
Charles Neider's _Life as I Find It_. This is the text of a letter
published in the New York Tribune, January 27, 1873 concerning the
incident on the Batavia in November of 1872.
I tracked this down via a reference in Dennis Welland's _Mark Twain
in England_ page 53.
Paul Berkowitz