Actually, there's this one bizarre rule whereby traffic coming from the right on an "equal" crossing or junction (no indicated priority for either road) has the right of way.
It's the same in the US. From the NC Driver's Handbook:
In reply to:

In intersections without traffic signs or signals, the right-of-way rules state that:

  • the vehicle already in the intersection has the right–of–way ahead of any car that has not yet entered;
  • when two or more vehicles reach an intersection at the same time, the car to the right has the right–of–way;
  • a vehicle with the right–of–way may move straight ahead or, if legal and after signaling, turn right or left; and
  • even with the right–of–way, be careful to avoid hitting other vehicles and pedestrians.
When two facing vehicles approach an intersection at the same time, the right-of-way rules are not much help. Both drivers can move straight ahead or turn right. If one driver is going straight while the other wants to turn left, the driver who wants to turn must wait. The driver who wants to turn left must give the proper signal and wait until the turn can be made safely. Therefore, in this case, the driver who is traveling straight ahead has the right–of–way. Never change lanes while you are moving straight ahead through an intersection.

(God, I hate the limits of the markup on the BBS.)
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Bitt Faulk