According to The Other Wiki, Clara from The Torture Garden is only referred to by her first name in that book, so the surname was provided by Newman. And I can't believe he didn't intend it to be a reference. (The other character he gives a surname to is Phantom's Carlotta, who becomes Carlotta Castafiore to suggest a connection to another self-obsessed opera diva.)
But I've no idea what the reference is meant to be, especially since there's one particular Watson who rather dominates the name in Victorian literature. And the only connection I can find there is that in the Sherlock episode "A Study in Pink", Clara is the name of Harry's ex who gave her the mobile phone that she then gave to John, and one could therefore work backwards and declare the original H. Watson must have an ex called Clara as well. That seems a bit weak, though.
Anyone got a better idea? I think the bit at the end about her being in Cambodia must be significant, but it's not helping my Google-fu any.
- Something that might be worth stating explicitly is that she's Mrs. Clara Watson, which suggests that rather than a direct reference we might be looking for a man named Watson who could conceivably have passed his surname to her by marriage. I agree that it doesn't seem likely to have been the unfortunate H. Watson. (Unless it's meant to suggest that Clara gained her British citizenship the way Modesty Blaise was once said to have done, by way of a marriage of convenience to a penniless alcoholic Englishman who conveniently died shortly thereafter. But that seems roundabout even for Newman.)
- The character's name was only given as "Clara" in the original novel (published in 1899) but she was given the surname "Watson" in the 1922 play based on that novel.
