Quiz - 17

At the recent inter-departmental jam making contest, four lucky candidates took part to make the juiciest strawberry jam. The ages of the contestants were 14, 17, 20 and 22. As it happens the person who came last was the oldest, whereas Stuart was three years older than the person who came second. James was neither the oldest nor the youngest and Kev finished ahead of the 17 year old, but didn't win. John was also unlucky this time and didn't win either. Can you determine who finished where and how old they are?