"Can I buy you a pint, Sir?" came the words from behind me as I queued at the bar of a crowded city-centre pub one Friday evening. I did not recognise the voice, but very much welcomed the sentiment and looked over my shoulder.
The voice belonged to a tall, smartly dressed, bespectacled 30-something man who smiled in an amused way as he clearly had me at a disadvantage.
"It is Mr Davies, isn't it? You used to teach me ... it's Lee."
I sought another clue to help me in my mental search of the many Lees I have taught (a number that must be approaching 100 or so).
I apologised for not recognising him. He was in no way offended and instead seemed to enjoy the game; he still did not offer a surname, but continued to tantalise me with further titbits of relevant information. He eventually reeled off a list of his contemporaries and classmates.
This read like a sort of rogues' gallery of my ex-pupils from the mid-1990s. Some of these were names that I would certainly be unlikely to forget, and some probably inhabited my nightmares.
It was then that the main cause of my confusion dawned on me. My first impression of my new companion had, in my mind's eye, caused me to picture him as one of the school's foremost alumni. Or maybe he was a high-flyer who had been an academic success at school but had somehow been off my radar at the time. The list of his classmates indicated that this was probably not the case.
The young man who I spoke to that evening was charming, articulate and seemingly doing all right for himself. He later told me that he owned his own business and that his BMW was parked outside. I guessed that he probably earned considerably more than I did.
The Lee who I taught 15 years earlier I eventually remembered as a rather awkward, unmotivated, occasionally disruptive member of a dedicated special needs class (the word "inclusion" was not then part of the educational vocabulary) that certainly fulfilled the rather euphemistic term "challenging".
I vaguely remembered detentions, critical reports, phonecalls to parents and certainly not a pupil who I would have described as a pleasure to teach. However, here he was, keen to buy me a drink and to reminisce.
His memories of school were overwhelmingly positive, though he was not blind to his own shortcomings, and he was so, so grateful for what his teachers had done for him.
Rose-tinted spectacles? Maybe, but it struck me that here was someone who I had not obviously helped to any sort of academic or other form of traditional success in school.
Yet somewhere along the line, my colleagues and I had pointed him in the right direction or supported him in some way. He clearly realised that, without this help, things might have turned out differently for him.
Similarly, I am still in touch with a group of ex-pupils (most of them ex-members of my choir), some of whom would once have seen me as their nemesis. One of them memorably poured a glass of water over my head in a particularly heated moment on a foreign tour to Barcelona; another spent most of her GCSE year playing truant from my class.
However, the same people now come back to perform in musical activities in their old school and are only too happy to help out at the drop of a hat. The angry words and events of the past seem a distant memory, and I like to think that I can number these young people among my friends.
And so the next time I have a particularly difficult time with an unresponsive or insubordinate pupil, or am told where to stick my conducting baton, I will try to imagine the same individual at the bar 10 years down the line. Make mine a pint of bitter, please.
Geraint Davies is head of the arts faculty at Llantarnam School in Cwmbran.