Actually, I think he did have an IR! I can't ask him now as he's no longer at the school having moved on to the North Sea. Illegality to one side, I suspect the rationale was to demonstrate what it was like and to make sure I never did it. It worked.
This wasn't on a grey murky day but a very sunny day with only a few small clouds and it wasn't for very long!!! I don't know whether that mitigates it or not - just that those were the conditions.
Cheers
Whirls