what age do you think is suitable for a child to play outside by themself?

now im not talking walking the streets.
we live in a block 4floors high we are on the top. its a fairly decent area in islington

at the rear of the flats is a playing field where all the kids from the flats play.
its not big at all. we can see the play area out of our rear balcony.

our son is 6 and keeps asking if he can go down to play with his mates from school.

im not happy or comfortable with this so he doesnt.

i go down with him and let him play for aslong as i can be bothered to stay down there for.
usualy until 5.30ish as im bolloxed from work

i feel quite bad for him when i take him up as his mates are still down there but i wont allow him to play down there unless either my partner or me is there with him.


at what age would you feel comfortable letting your kids out alone?


am i being over protective?