I'm struggling to believe that a Captain would announce to passengers that "we have about five to 10 minutes’ fuel left so we may need to divert to Gatwick". If you want to cause instant terror that's a good way of doing it, especially when it's pretty obvious that to get to Gatwick and land within the next 10 minutes is probably impossible.
PPrune's resident experts would immediately know what he meant. Many others would guess. But it's a very ambiguous announcement if you know nothing about how airlines do things.