The problem is, technically the guard was in the right, since the vestibules are considered First Class accomodation, and even if standard is full the guard doesn't have to let you in first class, but they can do if they want. Of cource, if standard class was so full that there was hardly any standing room, then I can't see why he didn't allow you to stand in first class. Then again, you get jobsworths everywhere. I often wonder aswell if the jobsworths are the same people who will be first to twist rules if it benefits themselves or friends/family, and are the sort who are just as bad when in situations where they are the customer. Wouldn't suprise me at all.