Meeting Former Neighbour

I lived above a married couple for four years. They had a baby during that time and would often have a nanny come around during the week. We sold our respective properties at the same time, nearly a year ago, and moved away to different parts of London - without knowing where each other had gone. I moved into a large building, split into six flats. A fortnight ago I was off work ill and heard a car come onto the gravel drive. I looked out of the window and recognised the make and model as the one my previous neighbours had owned. The car stopped and after a while the driver's door opened. Out got my former neighbour. She entered the building and I heard voices. A moment later she came out of the building, so I went out to say hello. We had the usual "what are the chances of this" chit-chat and I asked what brought her here. It turns out the woman who lives in the flat opposite mine - who I befriended upon moving in - was my former neighbour's nanny. It was she that had been around to our old flat those years ago. It was only because I was off sick that day that I saw my former neighbour. Of all the millions of people in London, what are the chances that my new neighbour was my former neighbour's nanny. Spooky.