Sorry Simon, I apologise. But having photographed cats for more years than I care to remember, your photo did look as though it was a compilation from more than one photo.
I think you need to be a little more careful when cloning out background as it does seem to be a bit harsh and the edges too defined on the paws of both cats.
As to how "we" knew it was you first upload, we looked at your profile which states you have/had only uploaded one photo. Continue with the good work and welcome to EPZ.