Circular concrete blocks were used during the second world war to block roads and create check points for vehicles and pedestrians. Technically, they are known as 'anti-tank cylinders' the cylinders were placed upright so that the holes or sockets could take a 'barbed wire picket post'. Souce "20thC defences in Britain CBA.
At Great Asby they have been used use as riverbank reinforcement on the side of the village beck.