The Union Flag flying outside the R.U.C. (Police) Headquarters in what is supposed to be Belfast is upside down.
Princess Diana did not actually appear in this episode in the form of a cameo, which would mean she actually was on set and filmed the scene with the actors. The scene of her walking through the airport when Rabb and MacKenzie are there is just a reused media footage clip taken by reporters.
Although this episode supposedly took place at Holy Loch in Scotland, after the collapse of the USSR, the US Navy closed its submarine facility at Holy Loch in March 1992, five years before the first airing of this episode.
Inspector Hutchinson, when addressing Lt. Nevins, pronounces her rank incorrectly for someone who is Irish and a citizen of the UK. The United States is one of the few English speaking nations that uses the pronunciation 'loo-tenant'; almost all other nations, including Ireland and England, pronounce it 'lef-tenant'. Even when addressing American officers they still use their pronunciation of the rank, it is what comes naturally to them, and there is no expectation that they have to pronounce it differently.