Thanks Ryan

That's certainly true, but it then raises the question, which one is landing? Are they both landing? or is the aircraft that is on the long final really landing, or just doing a fly by, or whatever.

It won't do much good at any inquiry to claim that you thought the aircraft on long final was just doing a fly by, or whatever. Anyway, an aircraft on a base leg is obviously not on a final approach.The full extract from the link I quoted covers this point in (2).13 (1) An aircraft landing or on its final approach to land shall have the right-of-way over otheraircraft in flight or on the ground or water.(2) An aircraft shall not overtake or cut in front of another aircraft on its final approach toland.(3) If an air traffic control unit has communicated to any aircraft an order of priority forlanding, the aircraft shall approach to land in that order.(4) If the commander of an aircraft is aware that another aircraft is making an emergencylanding, he shall give way to that aircraft.Of course if there's any danger of collision you give way regardless of right-of-way but by everyone following the rules the risk is minimised.

Where does a final approach begin?I've heard people radio a 5-mile straight-in gps final approach. Would that count?

I'm not sure how you would do it in the US but in the UK you'd make a call downwind, and on base leg so that other pilots around your are aware of your position. Likewise the pilot on final would do the same.You keep a good look out. If I was the one down wind and I was aware of the situation arising I would slow the aircraft down to 70kts and make a judgement. If I was still getting close I'd do an orbit and rejoing the downwind legand continue as normal.

I am a real-world pilot and I always think of the red and green wingtip lights as "traffic lights". If you are at the same altitude and you are on the green side (you see the green), you have the right away -- and if you see the red (are on the red side) you need to yield. Regardless, if an aircraft was on final, I would extend my downwind.