Yep, closed on 3 sides that's why workman said it doesn't need planning permission which seems questionableActually, you can't trespass the eyes. If the Op can see it, he can photograph it.
IMHO it could be debatable position wise, there are rules concerning distance from the boundary and height.
It looks to be a good 3M? the guy is half a metre up on a ladder, and if he's 6 foot there's a long way to the apex.
The good news? is that the front looks to me to be intended as being left open.
therefore not a drum practice room or gym.
Hopefully just a covered shelter.