The 3P+N at the bottom right could be unused, although why the N isn't with the others IHNI.
The incoming to the switch could be the black cables at the top and the mess at the bottom left some kind of dodgy joints to the black cables running up to the grey box below the trunking, or the incoming could be the BBG at the bottom and the black cables to the box nothing to do with that. But in that case you'd have stuff in there not isolated by the switch.
All that foam could be to seal cable entries or it could be to envelope manky joints.
There's a significant discrepancy in sizes of conductors connected to the top of the switch.
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