The government's broader argument is diplomatic. For years the UK has been accused by friend and foe alike of hypocrisy; for making the case for international law on the world stage but ignoring it with regard to the Chagos islands. How could the UK criticise Russia for breaking international law in Ukraine and China in the South China Sea if it was itself breaking the rules in the Indian Ocean? Ministers also argued that at a time of geopolitical uncertainty, when old allies were less reliable and new partnerships had to be formed, the Chagos row was a diplomatic boil than needed to be lanced. It was notable the UN Secretary General Antonio Guterres issued a statement welcoming the deal, saying it demonstrated "the value of diplomacy in addressing historical grievances". Again, the government's critics dispute this conclusion, arguing the world has changed, and that we live in a time when "might is right" and close adherence to the fine print of international law is outdated and a geopolitical indulgence. Would US President Donald Trump or French President Emmanuel Macron, they ask, give up territories overseas? The government's response to that challenge is to say that the US - which largely runs and pays for Diego Garcia - now supports the deal with Mauritius, despite earlier doubts. US Secretary of State Marco Rubio said "following a comprehensive inter-agency review, the Trump Administration determined that this agreement secures the long-term, stable, and effective operation of the joint US-UK military facility at Diego Garcia". Other members of the Five Eyes intelligence alliance also back the agreement; the base is a huge hub for the exchange of global signals intelligence. These issues will now be tested in Parliament as MPs consider whether to ratify the agreement. The government may win the vote because of its majority. But it has yet to win the argument.