It reminded me of a recent realisation that you never see kids climbing trees these days. I used to be a whiz at climbing trees - it might have been the one sporty thing I did best. I had a long reach and I was quite light, plus I was brought up in a heavily wooded area. There was one huge purple beech that I was always up, and having climbed it to the top once, I knew every foothold and reachable branch so that I could clamber up in a matter of seconds, then spend a couple of hours in lofty isolation watching my parents wonder where I was through the canopy of leaves below. I even slept in it at one point - without falling off - cradled in a matrix of branches which supported me perfectly.
You could say that today's Health and Safety obsessed environment (in my day, we were obsessed with Health and Efficiency) forbids tree-climbing without a harness - it does, actually - but I think it is more to do with a general attitude to settees and pizzas.
Going up is always a lot easier than going down. Going down was where the panic set in for the average schoolboy, but you could always be talked down by a terrified friend waiting 40 feet below you - terrified about being told off for allowing you to break your neck without intervening to stop it.
For me though, tree-climbing was a solitary experience. It is another world up there - easily reachable from the ground and yet so far away from it.
The other thing is that (as Bonny Prince Charlie worked out) it is amazing how hardly anyone ever bothers to look up. You can sit comfortably about 20 feet above the heads of hostile adults and listen to them as they discuss your downfall, trying to stifle your laughter at their stupidity.
Almost nobody who had not been previously warned about it noticed the new pub-sign I (and my glamorous assistant) have made recently, but just walked beneath it as they did with the old sign on countless occasions. Even my glamorous assistant did not know of the existence of the old sign, which had been swinging above his head for about 25 years.
I used to look up far more than I do these days since I developed some sort of arthritic neck, but I still remind myself to crane upwards on a fine day, and there is always something to see.
A buzzard circling on a thermal - a distant dot, half a mile above. A stratospheric weather balloon - a little white dot at the edge of the earth. An airliner passing through at 50,000 feet usually sparks off a competition to guess the exact quantity of complimentary peanuts on board, between me and whoever is with me at the time. 'Warning - May Contain Nuts'.
I once looked up into a clear, blue, summer sky to see a meteor flash into our atmosphere, leaving a straight, white trail behind it which hung there for three minutes. You can see Jupiter in broad daylight - if you know where to look.
I wonder how many alien angels have crept beneath the radar as we have slept, or walked with our eyes in the gutter, looking for dropped coins.