There is no national interest in the Chagos Islands or Diego Garcia. If there were true national interests then Diego Garcia would be a British base not a US one, handing such security over to the US clearly shows that the UK does not have sufficient national interests at stake to maintain a base on the islands themselves. Moreover if it is in the national interests of the United States to have a base there is little reason to assume that the US could not negotiate similar terms from the government of Mauritius as that of the UK to secure those interests.