It's been rumoured for some time (and says on wikipedia) there there were potentially air raid shelters under Green Gate Common (the green space opposite Ducketts Common just off West Green Road).
I'd much appreciate some insight or information if anybody has any, and thought where better to find out more than Harringay Online
Thanks, Etch. Good find. I think you're right, which suggests that rectangle on the 1947 map may have pre-existed the age of air raid shelters. From what we can make out of the 1937 photo, it looks more like an old style seating shelter.
This edited version seems to support the seating idea. It seesm to show two arch-shaped openings