How to make friends: unusual ways

Here's a short timed and rapid tour of England, not Britain, just England: https://expatexplore.com/tours/taste-of-england/
and it's an American who's told me of it because she and her husband are about to do it. They arrived in London last week, and husband and I went to meet them. We had never met them before but got on well, chatting from our meeting point outside Buckingham Palace, then as we walked to Brown's and while we had lunch.
This is my new random friend (RF). RF emailed me some years ago, "Dear B..." which isn't quite my name. First I thought it was spam mail, then I realised as she sent me more emails that she had the wrong address. I ignored them. Partly I ignored them because she was emailing me at an email box that I rarely used, so I didn't notice them for months. Over time I got to know something of her life as she told it to her friend, B, Then one month I looked at the email and saw that she was telling B about some issues, issues that touch your heart. At this point, I had to tell her that she was emailing the wrong person, but that since she'd told me so much about herself for the last two years, here was some information about me. She thanked me. The next New Year we exchanged emails just to say hello.
A month ago I realised that RF was due a big birthday this year so emailed to ask her about it, and she emailed back to say that they were coming to England this month, to visit on a whirl wind tour, including a couple of days getting over jet lag in London, and then this expat tour. It was too goo an opportunity to miss, so I suggested we met. We didn't even know what we each looked like and she sent me a photo of her at that big birthday.
I can't tell you here how much we've got in common with this lovely couple from Detroit., but we are both glad she made that serendipitous typo in that email to Betsy and we'll be keeping in touch on purpose in future.
Telling this story to a tae kwon do friend today she replied telling me of a occasion to do with random theft, when she made a new friend, one that she's kept for twenty years. We meet nice people when we respond well to random opportunity