Conversation so far:
What did Denny Hulme do after leaving F1?
After leaving F1, Denny Hulme led the GPDA (Grand Prix Drivers' Association) for a brief period.
Why did Denny Hulme only lead the GPDA for a brief period?
The cut and thrust nature of the post was ill-suited to Denny Hulme's gentlemanly nature and he did not fill the post for very long.

Question: What did he do after leaving the GPDA?
Self-contained rewrite: What did Denny Hulme do after leaving the GPDA?