What is this in my wall?

[Wallquestion159]

Why is it black? I just expected brick as it on the other side of the room.

The brick has been chased and then concreted over looks like

Looks like breeze blocks instead of brick? (The grey ones)

Ah the chasing and concreting over makes sense as there would have been plugs in different positions over the year.

I just hare uncovering weird things as my mind starts panicking about asbestos! The electrician didn't mention anything, I've just noticed it now he's left.

I think the grey looks like breeze block too.

I just googled breeze blocks and I think you are right! I have learnt something new today!