This time, it triggered a memory cascade. When I was young, we lived for a while right up North in Redcar, and we lived opposite a park. Walking along that path gave me a definite feeling of congruence with the park opposite our old house. From there my brain skipped forwards some years to the time, when I was about 12, when (for some reason that escapes me) we visited Redcar for a weekend. We revisited that park, which had changed, but was still recognisable even from half a lifetime's distance. My parent's also visited the parents of someone I'd known quite well for the few years that we'd been there. Looking back I'm surprised, although it seemed quite natural then, I didn't recognise her at the time - 6 years changes anyone - but it was clear to us both after only a few minutes that we were still the same people we remembered, and it was as if we hadn't not seen each other for 6 years.
I wonder if there's anyone I haven't seen for 13 years now (or even 6 for that matter), with whom I would have the same resumption of tone of interaction; I don't think there is though, at least not of people with whom I spent so much time with at the time.