I have another article on Comment is Free this morning - I am told it almost made the printed edition of the Guardian:
This shrinking of the child's world has had numbers put on it by the filmmaker David Bond. His mother, he calculates, roamed across 50 square miles at the age of 11, but as a boy in the 1970s he was confined to just one. Today, his son and daughter do not leave the garden unaccompanied.
Books for children reflect this narrowing. Where adventure stories used to depict a landscape alive with youngsters finding buried treasure, thwarting robbers and rounding up Nazi spies, the constraints on modern children mean authors must now invent whole fantastic worlds before their young heroes can enjoy any freedom. It's not just outdoor play that has disappeared: a whole school of literature has died with it.