Found on top of a mossy dry stone wall, about 4ft high, between rushy improved pasture and acid grassland/ grass dominated bog.
No interactions present.
I showed this to a colleague and she thinks that a bird or mammal probably caught a frog and took it up onto the wall to eat it. They leave any spawn as it expands on contact with water and would do so in their stomache..
I'm happy with that answer!
Lat/Lng: 55.5295, -4.2353
OS grid ref: NS590284