There seems so be directional light on the foreground rocks and there's plenty of detail in their shadowy crevices. Perhaps the long dev time was to preserve this without destroying the very soft contrast of the misty background. Otherwise the rocks might have been disconcertingly theatrical.
This is only a guess; the actual scene may have been quite different. For all we know this may have been developed in a batch where the others needed this development.
Your description of the weather conditions are correct David, not as bright as appears in the image, I needed to make sure I captured the shadow detail by giving extra exposure at the same time the light in front of me was so soft and delicate, so by using the semi-stand method it has retained detail exactly as I wanted.
Now if I had used my normal time for Pyrocat 1-1-100 16mins, agitation every minute, would it have turned out the same, I don’t know, I think I have better edge definition, what I do know is it did work well, creating a negative that preserved detail in both low, mid and high tones.
Martin, a lot may have to also do with the volume of developer used per sheet that can make a huge difference with extended development times if the developer is starting to exhaust. I know that in my Jobo 2000 (inversion) tanks 1 hour development would be excessive even with minimal agitation but I'm using at least 250ml of developer per sheet.
My own experience is I get excellent edge definition with normal inversion agitation, Pyrocat HD is the only developer I've used in the last 10 years but I first started using it around 2004. I switched completely to Pyrocat because I found it superb at handling all sorts of lighting conditions particularly quite tricky ones.
So what works for you might well not work for me and at the end of the day it's what works for us individually.
I agree, Pyrocat HD is a wonderful developer probably the only one you need for most popular films, I particularly like it with 4x5 Trix.
Last weekend I went out to the Ilkley moor with my Holga, I use ND filters to get me in to split seconds, I made a mistake thinking I had an 8 Stop ND when in fact I had fitted a 3 stop ND, all exposures we’re over by 5 stops, to say we’re a little dense is an understatement, however I developed them in Pyrocat with semi stand, scanned them in my Nikon 9000ed, this took around 1 hour to scan one frame, the results can be seen here. http://www.digitalmonochromeforum.co.uk/threads/ilkley-moor.4192/.