Watching us were three deer standing camouflaged in the grass near those concrete blocks but it was too hard to get a good photo of them.
In 1940 the fear of invasion by German troops had prompted coastal defences to be built along the east coast of Britain.  Thousands of huge concrete cubes were made and arranged in long rows, often several rows deep, to form anti-tank barriers at beaches and inland and sometimes smaller numbers were used to block roads.  There are still many visible in East Lothian including hundreds here on the Nature Reserve at Aberlady.  Much of the area beyond these tank traps used to be sea so if any invaders had managed to land on the beach they would have been funnelled into this V shape via a mine free section of beach.  Then they could be attacked with machine guns and mortars.  A further line of traps extend behind the sea buckthorn.  Fortunately there was no invasion. 
Other war defence remains are here and here and here and here.