https://www.openstreetmap.org/way/26713924/history  . I see Edward swapped out the prison tag in 2017, and  in 2019 it was re-labelled as "Holloway Prison Site" which helps make it clearer that it's not a prison. So that answers the question in this note.
Recently going past on the bus I've noticed construction fences. Maybe we should change this this to landuse=construction. That's the only I can think of fixing at this stage. But then of course it would be good to survey the pricise extent of the construction site.