A significant plot point in the game is that you have to collect money for King Richard's ransom, which then gets subtracted from your total funds past a set occurrence in the game.
I have replayed this game to completion many times over the decades, but I have never actually been out of pocket at that critical moment. My impression is that it's mechanically impossible even if you win missions haphazardly and spend as much as possible within the game's parameters. In fact, no FAQ author that I could find seemed to know the answer either.
Is it actually possible to be in a situation where you cannot pay? If so, what happens?