According to declassified documents, during the Falklands War, Margaret Thatcher got on the phone with French President Francois Mitterand and demanded the codes to the Exocet missiles that the Argentines were using to wreak havoc on the Royal Navy. Thatcher threatened that she would order a nuclear strike on Buenos Aires otherwise.
I know this is near-ASB, but if she was crazy enough to actually do it, what would have been the repercussions?