I WAS at Glasgow Queen Street the other night, just about to climb on board a train, when a bloke in a suit, just about my age, materialised at my shoulder.
I knew it was just a harmless slip of the tongue, but I paused before answering and tried to think of something witty and original to say.
Forty-eight hours later, I still haven't come up with anything.
You know you're getting old when you've lost that ability to deliver a decent comeback - and envy those people who are more than capable of thinking on their feet.
There was a lovely example of this a couple of days ago when someone chucked a banana onto the pitch in front of Barcelona footballer Dani Alves, just as he was about to take a corner kick.
I loved his reaction. He didn't get upset, or angry, as was his right. In swift order he picked up the banana, unpeeled it, ate it, threw away the skin, and took the corner. "Utterly brilliant reaction from Alves," Gary Lineker tweeted. "Treat the racist berk with complete disdain."
If you're in the public eye you risk attracting oddballs, online trolls, and, in Alves's case, worse. I don't know how you deal with that sort of attention, but lots of celebrities on Twitter have a talent for spirited, witty comebacks and putdowns.
Actress Gabourey Sidibe endured lots of snide remarks about the dress she wore to the Golden Globes awards, but got her own back.
"To people making mean comments about my GG pics," she wrote, "I mos def cried about it on that private jet on my way to my dream job last night."
When one Twitter user was unwise enough to write dismissively about James Blunt, the singer snapped back: "You obviously went to one of those schools where everyone got a prize."
Blunt is one of those celebs you antagonise at your own risk.
When one tweeter wrote: "James Blunt just has an annoying face and a highly irritating voice," Blunt added: "And no mortgage."
And when someone else asked him: "Why you only got 200k followers?", the singer replied: "Jesus needed only 12."
Best of all, though, was when someone tweeted to actor Frankie Muniz: "Ur acting is just awful. Sorry, but it is."
Frankie's cutting response? "Yeah, but being retired with $40,000,000.00 at 19 has not been awful. Good luck moving out of your house before you're 35."