This is an old question that is no longer in use.
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Is it true that the priority road ends before the junction with A?
Priority road signs are usually posted after a junction, but this does not matter in this case, as the question is asking whether the priority road ends. It only ends after the sign. As additional proof of this, there is a give way line at A:
Give way line (M14)
”This marking indicates the line that a vehicle should not pass when the driver is observing the obligation to give way.”
More examples of explanations: