Willow's tend to have that diamond shaped pits. What species of Willow this one is I can't tell you.

Ash, white ash particularly, forms diamond patterns in the bark, when its semi mature - eventually turning to deep ridges in fully mature ones. This picture though, looks as if something's adhering to the bark, as if something's poured down it and set.

Ah...Thank you, there are lots of Ash trees next to it, none with this bark though...the weather is pouring down on it Bamboo, The trees here are almost entirely covered in moss it is so moist,

You are better to go by leaf shape to search what type of tree it is. I still think Willow but am happy to be wrong!

I will keep an eye on it Kildermorie.