I'll add my ten pence worth robert.
A strong 'type' whippet shouldn't exist IMO. A whippet type should merely be a true to conformation whippet, nothing else.
However, a strong whippet does exist. There are a few lines that spring to mind but the ones mentioned are not necessarily in keeping with your question. I have seen some very game, very fast MB dogs, but a few quite small ones with the hearts of lions. I have also seen some big strong, great looking whippets with the hearts of mice.
Your Prince is an example of a strong whippet. My Merlin might have been if he managed