They Shall Not Pass?

Are these WW2 defenses or are they to keep the holiday makers in their place?

The number of concrete blocks and their closeness is a surprise. And such an intensive amount of work especially when you consider how many miles they extend. 

It is not surprising that they were not removed after the war ended when there was so much rebuilding to do.  And now they are a curiosity, especially the ones that have been eroded away from their original positions and lie haphazardly on the beach.  Perhaps these are oddities more so for younger generations who are so much further from the events than mine was.