I used to run it in 22 mins 2 years ago (age 45). I had never been 'athletic' as a kid, was always picked last in gym, and as a result had always avoided sports. I didn't start running until 35 when I found out about weight bearing exercise, age and bone production.
I was happy with my 50 minute 10k race, but when I married my husband say "you can go faster", and wrote me up a training plan that magically worked. It's amazing what can be achieved with a more scientific approach to training.
This year I'm nursing some sort of long term hamstring tendinitis, so I just jog around the block with friends, talking, at about a 6 minute K pace.