Andrew Martin: We're so afraid of dying, we don't dare live

A boy of primary-school age looking along the shelves of a bookshop would be relaxed at the sight of all those titles advertising "A 1,000 Experiences You Must Have Before You Die". He has plenty of time to get round to seeing the Taj Mahal at sunset or having sado-masochistic sex in the Reeperbahn. But if he noticed the list released this week by the National Trust headed, "50 Things To Do Before You're 113/4" then he might have felt the pressure was suddenly on.

The trust's injunctions reflect a report it has commissioned, which indicates that a quarter of all children never play outside, a third have never climbed a tree, and one in 10 can't ride a bike. This because they're spending four and a half hours a day in front of a screen. I was not a particularly hearty child myself. In fact, I spent much of my schooldays swotting in York Reference Library, as did my arch academic rival, and I made a point of never leaving before he did. But, looking at the NT list, I had done almost everything on it by the time I was 103/4, let alone 11.

Playing conkers, for example. If it was autumn, that's what you did, always making sure beforehand that "stampsies" were allowed – that is, if your mate's beloved vinegar-conditioned sixer (it had won six matches) fell off its string then you'd stamp on it. You had to get that in writing, because a purely verbal agreement never seemed to stop you getting beaten up if you exercised your right. Building a den? Of course, you built dens in the local woods, always with the idea of relocating to them full time, or at least spending the night there... which never seemed such an attractive prospect when seven o'clock rolled around, and The Man From Uncle was on the TV. Rockpooling? In summer, you spent half your time clambering about on Filey Brigg, that barnacled promontory at the south end of the bay. I was encouraged in this by my dad, who had practically been a professional rockpooler in his own youth, and who taught me you could get a limpet off a rock only if you did not come between it and the sun, thus triggering its defensive light sensors.

It's not so easy to do the things on the list as it once was. On Filey Brigg, there's now a sign saying "No Safe Access". Of course, there's no safe access. That's the whole reason the 10-year-old boy is there! And conkers has been frowned on ever since 2006, when a headmaster in Carlisle required his pupils to wear goggles when playing. Health and safety is taken to be the impediment to an outdoor childhood, but I wonder....

I was in India two weeks ago, where boys will still be boys. I came out of St Paul's Cathedral in Calcutta, and saw a lad of about 10 holding two strings, which rose up vertically towards a red kite that seemed to be a 100 feet above the vertiginous central tower. Of course, he was grinning hugely. In a jungly region of the north-east, I looked 70 feet up a gnarled banyan tree and saw a small boy testing the safety of a branch. In a town called Tinsukia, I saw two boys playing tag on the flatbed trucks of a moving freight train.

In India, it is often said, life is cheap. But it is also religious. I do not endorse playing tag on freight trains, and I note that is not being suggested by the National Trust, but perhaps the main difference between the safety-first childhoods of today and the freer ones of the past is our relatively recent secularisation. Life must not be even slightly risked, because there is nothing else.

Andrew Martin's book 'Underground, Overground: A Passenger's History of the Tube' is published next month