There was a man on Radio 4 this morning from some kind of official flag society who was going on about how often the Union Jack flag had been shown upside down in the Olympics. Now you would think that someone like this would know better but I have to say I think he is wrong. Unless all of the flags that you find through sources on the internet have been recreated unsuccessfully.
I have taken the wikipedia flag as the example I will use, as I hope it would be the correct one. You can find it here, but I have posted a copy below to prove my point.
With the Union Flag, if you look at the top right section then the wider white bit is nearer the middle, agreed? And when you go round the flag, each wide white section is positioned like the sails of a windmill, with the wide white bit in the same place (to the left of the narrow red bit as you look from outside the flag). So if you flip the flag upside down it looks exactly the same (I have put the word flag in so that you can see that I have flipped it).
However, if you flip the flag round horizontally then you will see that the thick white on the top right hand side is in the wrong position.
So, unless wikipedia (and plenty of other sources) have got their flag wrong then I can’t see how the flag can be upside down at all – if it was you would not be able to tell.