@Chris Bennett thank you! I’d assumed it was ivy growth, but upon closer inspection of the original file I think you’re right (I probably didn’t pay sufficient attention at the time lol). In looking at my original jpeg, which would have been converted from raw in lightroom, I noticed quite a lot of noise and smeared detail in the b+w version, so out of curiosity I tried a mono conversion through Raw Therapee…. wow, what a difference. Virtually all that noise gone and much better detail retrieval. Not sure where I went wrong first time round..
still, it was a while ago