Hi,
I don't know if this has been discussed before: Being interested in 
the various royal families of Europe I found the homepage of the 
Serbian royal family (www.royalfamily.org) where I stumbled upon an 
interesting passage:
"In 1944 in London King Petar (Peter) II married Princess Aleksandra 
(Alexandra) of Greece the daughter of HM King Alexander of the 
Hellenes. On 17 July 1945 while living in Claridge's Hotel Queen 
Aleksandra (Alexandra) gave birth to a son - HRH Crown Prince 
Aleksandar (Alexander) II of Yugoslavia.  
As the heir to the throne at that time had to be born on Yugoslav 
soil the British Government under the orders of the Prime Minister 
Sir Winston Churchill declared suite 212 in Claridge's hotel Yugoslav 
territory. His Holiness Patriarch Gavrilo of Serbia baptized the 
newborn Crown Prince in Westminster Abbey. His godparents were King 
George VI and the then HRH Princess Elizabeth now HM The Queen 
Elizabeth II." (
http://www.royalfamily.org/family/hrhcpa_bio.htm)
So a simple flight of rooms was made an enclave! The rooms above and 
belove this suite probably remained British territory?
But of course, the question remains whether a state can "declare" a 
part of its territory as belonging to another one? Could the U.S., 
for instance say: "Hey, Point Roberts is too much of a fuss for us, 
from now on it's Canadian territory!" Even if all residents of PR 
agreed it probably would not automatically be Canadian, without their 
government agreeing to it.
Does anyone have an insight into this?
Greetings,
Anton Z