Rudi, thanks for a quick answer...
Does this mean that when ending your RTW trip you must go straigth back to your origin/end city, without touching any other city in that continent?
What is exactly the reason?
As far as I know the restriction are ending in the same country. There is also something about no stopover more than once in the same city.
Is it because of just connecting through and already used city (eg Frankfurt)? If this is the reason, they I can probably workaround be flying through other cities.
Another example: Starting in London, heading west to USA, then Asia, and coming back to Europe on Singapore Airlines to Madrid. If you are right then this last leg should'nt be valid, since I'm already in Europe.
If your are right, then I will need to completely rethink my holidays.