As a Primary school aged child I played in Hackney on bomb sites. Had some wonderful hiding places to put messages in these.
By secondary age I was living in Harold Hill - East London overflow estate. Here we had woods, and fields to play in. Yes, gangs of us, quite mixed ages. One time my g.parents came to visit my us - long walk from nearest station, and reported in horrified tones to my parents that they had seen me hanging upside down from a tree (not appropriate behavior for a 13-year old girl!!!!)
Great times, during school holidays we would go out early in the morning, and, except maybe for a quick trip back home for a snack and a drink, play together until dusk. Not saying we did not get into some problems and trouble, including broken bones, etc. I can remember my 14-year old 'boyfriend' teaching me how to ride a 2-wheel bike. He used his older brothers (who was away doing his national service), so, the bike was a lot too big for me. The teaching method involved going up to the top of long hill, me sitting on the bike, and him giving me a good push. Few times of this, bike was not in good repair, but I had learned how to pedal enough to keep it going!!!