This is an interesting question, since the N.T. handbook states that amateur photography is welcomed at N.T. locations outdoors, and subject to certain conditions, at N.T. locations indoors (without flash).

The handbook also states that requests for commercial photography need to be approved through the Broadcast and Media Manager.

I think most members of  PoE would be happy to class themselves as amateurs. As such, at the time the the picture was taken, there was no intention to make a commercial profit from it. Now that PoE gives the option of selling an image, does this retrospectively make the photography commercial? Personally I think not, unless the photographer gets very lucky with a shed-load of requests. However, this could all be subject to legal interpretation,  so as Vince suggests, anyone who is worried might want to remove their N.T. images from sale. 

I would like to refer back to the initial post in this thread, asking for people submitting images to be a little more selective, taking into account the sell factor. To be honest, there still seems to be a delluge of similar themed pictures being submitted. In my view, it does take the "shine off" opening up the latest pictures. If I were a potential buyer, I might find it a bit hard sorting out the wood from the trees so to speak.

 POE remains very close to my heart, and the many images are still worth the trawl.  

 Interesting points about NT properties, as I have submitted quite a few pictures taken both inside and out at their sites.  In fact the very first one was of Chirk Castle, rather a long time ago now. 

  Hi C & S, indeed that is just what the doctor ordered, I am sure I will not be the first or last to forget to tick the box and there ought to be  some sorting the appropiate from the non- sellers- just got to see if anyone wants to buy any now.

                Many thanks.