In full view of every passenger was a teenage boy, on his way out for the evening, kissing his pretty girlfriend. And the whole bus groaned with envy.
I thought about it afterwards, and it occurred to me that the groan was nothing to do with sexual jealousy, but more to do with remembrance. Like many of those travellers that night, I have kissed pretty girls on buses. And I'd done so, oblivious of the scarcity of such moments. It was less the envy of the onlooker, than an empty feeling of loss.
You never know what you have... and so on.
Tonight, I was on my way into London on the Piccadilly Line. The tube was full of happy chatty Arsenal fans on their way to the Juventus game. I made eye contact with a few of them, and the excitement was palpable.
I thought about times long gone - the short trip from town to Trentside to greet Cologne and Puskas' AEK Athens side, the fabled trip to Anfield in 1978 for that finest of all hours (yes - I WAS there...).
I know that I should have felt happy for those Gooners. Outwardly, I joined in the party mood as the train sped towards Finsbury Park.
But deep down, I felt alone. Like a bereaved child in a room full of happy families.
Inside, I was weeping like a baby.