Could be one of the Middle East rulers planes, although these usually have a small flag somewhere on the tail. The Sultan of Brunei is also a regular visitor, but often goes into Brize.. .Here is his colour scheme, courtesy of Lee Collins. Yes I know it is only white on top!
<a href="http://www.leecollins.co.uk/v8ali.jpg" target="_blank">http://www.leecollins.co.uk/v8ali.jpg</A>
Image change to URL following later posting.
[ 28 February 2002: Message edited by: newswatcher ]</p>