A reasonable person
AC wrote: "Do you honestly think that the NSFW image that you linked to qualifies for "a reasonable person would consider the action depicted to be real"? I would like to consider myself reasonable, and to me it is obviously staged."
You can never put your faith in a law which can only be judged on the criteria of a reasonable person's views. People have hung on differing interpretations of reasonable, take Derek Bentley and the meaning of "Let him have it" http://en.wikipedia.org/wiki/Let_Him_Have_It
Re: Sooty, you are right in that this legislation is primarily a catch all. If you should cross any branch of authority you can expect to be investigated on some trumped up charge, which will come to nothing. But rummaging around on your computer is bound to find something chargeable, even if you have gone to great lengths to ensure that no one in any picture could be considered to be under 18, the extreme porn law makes anything else fair game for a prosecution.