Originally Posted by Calm down dear
many thanks for your help viajero, looks like a lost cause for my rtw.
Not entirely. While the 10 day rule is bullet-proof and cannot be circumvented, you might be able to live within the rules. Buy a separate roundtrip ticket trans-Atlantic, breaking your RTW in North America for a while. This gets you back to LHR on the date you want, while the RTW does not do the last intercontinental flight until later (up to 1 year validity).