If you ever come to the end of a road that has no road markings, you must be very careful. Regardless of whether you think you are on the road that has right of way, you must be prepared to stop. Defensive driving is about stopping and giving way if you are unsure.
Warning - Unmarked junctions can be very confusing. If in doubt, proceed with great care.
WHICH CAR HAS RIGHT OF WAY AT THIS JUNCTION?
When you come to junctions without road signs or markings, treat them with great care. Don't assume that you have priority at an unmarked junction - The Official DVSA Guide to Driving - The Essential Skills.
If you are unsure what to do at an unmarked junction, adopt a defensive style of driving and take control of the situation by giving way.