Or HP5, or Kentmere 400. Both seem grainier than TX and in the way this image is. I think the grainy sky is from high density in that area, since not much elsewhere. The light is a lot of it too. Presumably very low light, long exposure, reciprocity failure hitting the shadows pretty hard and boosting the contast. Plus a much higher brightness range than you might expect just looking at the actual scene. Deep shadows, skylight reflecting on windows and glaring on the cobbles, plus a relatively bright sky that was probably burnt down considerably.
I don't think anything exotic, but a good eye for light plus an understanding of the materials and/or good luck.
PS Good info on the printing techniques. Appeared while I was posting.