A few days ago, I sent something unusual through the post.
It felt slightly strange when I popped the envelope through the pillarbox, but that's what the instructions said I should do.
It's the NHS Bowel Cancel Screening programme. I won't go into details, but I had to do something mildly unpleasant but not painful, and send the results through the post. It's routine, you do it when you turn 60, then every couple of years thereafter. Today I got the results - "result was normal". So I'm good for another couple of years.