Conversation so far:
When did Stirling Moss return to racing?
Although ostensibly retired from racing since 1962, Stirling Moss did make a number of one-off appearances in professional motorsport events in the following two decades.
Where did Stirling Moss compete after he returned to racing?
Stirling Moss competed in the 1974 London-Sahara-Munich World Cup Rally in a Mercedes-Benz.
Did Stirling Moss win when he returned to racing?
Why did Stirling Moss leave racing?
On 9 June 2011 during qualifying for the Le Mans Legends race, Stirling Moss announced that he had finally retired from racing, saying that he had scared himself that afternoon.

Question: What happened that scared Moss?
Self-contained rewrite: What happened that scared Stirling Moss into retirement?