The bit where he took those three injured sheep for slaughter, and wanted to say a last goodbye only to find out they'd already been taken off and killed was such an unguarded moment. He was genuinely upset and unbalanced by it.

Of course, he later bounces back with the joke that he turned them into shepherd's pie, but that's just the Clarkson formula - shrug things off with a laugh and some boorish clowning.