PS Make sure you tell them you do understand that the thing in the FOM about viagra isn't such a big deal or anything to do with substance abuse.
It's actually because they don't want the captain (you) walking into the hosties briefing room and terrifying them with a massive boned-up mongrel tent-pole in ya trousers.
Not to mention the effect it'd have on some of the blokes amongst them.....
If you do mis-judge your viagra timing, just hook your hat on it during the brief.