I'm sure as a child I was walking to school on my own by the age of 7-8. I was certainly left in the care of my older brother (2 years 9 months older to be exact). All day in the summer holidays we were out. We lived in a ground floor flat and my Mum used to leave packed lunches for my brother and I on the balcony so we didn't have to go indoors. At the age of 5 I went camping to the Forest of Dean with the local youth club, sans parents (or older brother).
Things are so different now to when I was a child in the 70's and 80's. These days we seem to be molly coddling our children until BAM! they are teenagers demanding to be more grown up than they really are and often left to their own devices.
Mr.M and I are giving the 10 year old some more responsibility. We've started letting him walk to and from school on his own. It's about 10 minutes, there's no major roads but a few busy ones especially with parents trying to find parking spaces and zooming about in their bloody great four x fours that are needed for the wild suburban Surrey streets.
I've started letting him pop up to our local Tesco Express for milk & bread essentials - and letting him keep the change. He's walking the dog around the block, ensuring he has poo bags and doesn't let the dog off his lead.
I've also been leaving him for a short while too. I make him promise not to open the door to anyone. Any of us who need to be in the house have keys. A list of important phone numbers written down and the telephone. I'm not talking hours on end, usually only about half an hour or so. I take the 5 year old with me of course.
I didn't realise there was no "legal" age on leaving children. Although you cannot leave them if they may be at risk. I found this link here.
It's so hard trying to find the right balance of letting your babies grow up and start to spread their wings.