What are these?

What are these?

Observation - What are these? - Global. Description: I was out for a walk with a friend and happened to see these blue berries by the hedge. She's very knowledgeable about plants usually but she didn't know what they were either. As you can see, there's blackberries nearby but they look very different.

I was out for a walk with a friend and happened to see these blue berries by the hedge. She's very knowledgeable about plants usually but she didn't know what they were either. As you can see, there's blackberries nearby but they look very different. Are they just blackberry mutations or something else?