Requirements like this crop up pretty regularly, and while most cases are straightforward, this particular example had an additional wrinkle: instead of working with a standard lookup field, we are unable to say, for any given Task, whether it relates to a Lead or a Contact.
We have some new tools in our belt now, thanks to Lightning, which allow us to set up a fairly elegant solution. A simple formula field and a quick edit of the page layout, and we have the ability to give the client another reason to smile.
As is often the case, this solution will work equally well in Professional Edition as in Enterprise or Unlimited; there’s no rocket surgery here…