Story here. I guess the title says it all.
But of course, as with all things in the world, there’s a Thailand connection:
“These knives (or a near copy) are already being sold in the markets of Thailand. They cost 12,000 Baht (approx 180 pounds) and they are demonstrated by vendors on dead pigs or chickens. The resulting effects are horrific. It is only a matter of time before they reach the streets of the UK.”
Holy crap, it’s like Q turned into an evil mastermind.
…wait a minute…
Could it be this knife by any chance?
http://boards.straightdope.com/sdmb/showthread.php?t=476021&highlight=watermelon
Dang! I did a Search and did not see anything that looked like it. Foiled again. 
EDIT: I see my story gives a bit more info and a different angle on it, so maybe merits its own thread. But if the Mods want to close this one, I’m good with that.