The Sultan of Brunei has been a regular visitor to the UK and graduated from Sandhurst in 1967.
His son followed suit in 2011, when the Sultan stood in for Her Majesty the Queen during the passing out parade.
The Minister of State for Asia and the Pacific, Mark Field, told the House of Commons: "As many members will be aware, we have a specific responsibility towards British military personnel and their families who are stationed in Brunei, including as part of our long-standing garrison agreement which dates from the coming into existence of Brunei as an independent state in 1962.
"I can assure the House that we have the necessary protections in place with the Government of Brunei."
The MOD says the terms of the five-year contract means all personnel currently based in Brunei will be protected.