[twawaaay]

And this matches my experience.

I once joined a 10k without much research. It was on the weekend I wanted to run fast 10k (at the time that was 50 minutes for me) and I decided I might want to run it with other people.

The detail I missed was the race was organised by a local sports school to commemorate 50 years of the school and the participants were mostly alumni.

I quickly found myself at the end of the pack and even though finished around 50 minute I was still mostly surrounded by 40 and 50 year olds, everybody younger or my age was far faster than I was.