[Stuart]

Yeah, he has a TARDIS, being abroad isn't enough to cause him to miss things. Plus Donna was offered a UNIT job and Mel works there too, so they both also should be in the thick of it if anything happens. UNIT is part of the United Nations, their operations aren't limited to the United Kingdom!

Originally referred to as the United Nations Intelligence Taskforce, executive producer Russell T Davies said in 2005 that the UN was no longer happy to be associated with the fictional organisation and the UN's full name could now no longer be used.