Here are some 'Measured mile markers' (for measuring the speed of ships):
scroll down for the images.
http://www.geograph.org.uk/snippet/8651
I remember now that there were some tall ones at Blyth (or was it Newbiggin?). Don't know if they still exist.
If they are mile markers then there must be another pair a mile up or down the coast. (genius that I am
)
they also have to have a 'V' structure on one post and an inverted 'V' on the other and when they come together you see an 'X', then you start your stopwatch
These could have fallen off the posts you have photographed? just one bit left?