There are a number of inevitable signs of ageing. The odd ache here, the occasional pain there. The inability to get out of (or into) a chair without grunting. We expect this sort of thing.
But no-one ever warns you that your childhood heroes will - also inevitably - get old and start to pass on.
This was brought home to me a couple of days ago with the news that Lewis Collins, best known as Bodie in the late seventies TV series, The Professionals, had died at the age of 67.
For those of us of a certain age, this show has a special resonance. To explain, I have to take you back to Britain 35 years ago. It was a world of brown polyester. Politicians all looked about 100 years old. Newscasters spoke in measured tones, displaying carefully received Home Counties pronunciation.
If you were, like me, an eight-year-old boy, whatever TV you saw, on the three channels we had, was strictly limited. If you wanted to see a cop show - and let's face it, which eight-year-old boy wouldn't - you'd probably be faced with a succession of American imports.
Don't get me wrong. Starski & Hutch was great. But to this young Brit, it might as well have been set on an alien planet. People drove cars the size of small counties. They ate in diners where they'd casually toss dollar bills on the counter before leaving. There were a lot of guns. And inexplicably, they'd have telephones in every room of the house.
I was easily impressed at the age of eight.
But then The Professionals came about, and it was totally different. They drove Ford Escorts like that chap across the road. They had banter. Rather than gunplay, Bodie and his bubble-permed sidekick Doyle would normally give the baddies a quick slap.
It was a little shabby around the edges. It was grim and grey in places. It was ours.
On Friday nights, if we were very lucky, Dad would have have gone to the Boundary Chippy for our tea. We'd lie on the floor, all five of us gathered around our rented Granada TV, watching as the heroes of CI5 set the world to rights and winked at a lot of girls along the way.
And let's be honest. Who couldn't fail to have their eight-year-old mind blown by this?
I can almost taste the vinegar.
So farewell then, Lewis Collins. You and your CI5 colleagues made a big impact on me. Maybe I'll go and drive through some cardboard boxes next week, just as a tribute.
If you're around my age, you'll know exactly what I mean.