I have a crystal clear memory of getting on a train once with my brother when I was about 12 years old - that somewhat awkward stage of growing up where I was old enough to take notice of the world around me but not yet sure how to navigate its challenges.
Sitting opposite us was a middle-aged couple, dressed ready for the day and chatting quietly amongst themselves.
As we moved through the train and took our seats I noticed the couple start to stare at us, intently and with a look of bewilderment and almost disbelief.