Just read a 1989 Calvin and Hobbes strip about Calvin being deliberately left home alone, unwisely, for a couple of hours. Calvin is 6.
The NSPCC says there is no set legal age and “while every child is different, we wouldn't recommend leaving a child under 12 years old home alone, particularly for longer periods of time.”
https://www.nspcc.org.uk/advice-for-families/home-alone/
How old were you when your parents first let you be at home alone?
[ ] 8 or under
[ ] 9-10
[ ] 11-12
[ ] 13 or older, or they still won’t