Harry,
 >It seems that the island is leased!
 
I read lots of confused information about Diego Garcia ;-) I even read one 
article that was under the impression Diego Garcia was leased from 
Mauritius, so you have to wonder about how much research some journalists do!
I suppose it depends on how you define a lease, but the UK Government 
doesn't consider the island to be leased. In response to a recent question 
asked in the UK Parliament, the
Secretary of State for Foreign and Commonwealth Affairs replied...
"The United States pays no rent or makes any similar payment in respect of 
its right to use the British Indian Ocean Territory, including Diego 
Garcia, for defence purposes. However, in 1965, when it became clear that 
the costs of setting up the territory as a separate dependency would exceed 
original estimates, the US Government agreed to contribute £5 million 
towards these costs.
No part of the British Indian Ocean Territory, including Diego Garcia, has 
been leased to the United States. Under the 1966 Agreement between the UK 
and USA Governments, the islands will remain available to meet the defence 
needs of both Governments until 2016, and then for a further period of 20 
years, unless either side has previously given notice of termination."
The full reference is 
http://www.parliament.the-stationery-office.co.uk/pa/cm200102/cmhansrd/cm020513/text/20513w13.htm
The usual apologies for the lack of multipointing content.
Regards,
Kevin Meynell