What are the Brick-Built Structures?

Haseley water mill showing the main structure still intact but very dilapidated. The date of closure is thought to have been in the 19th century. Sluice gates and grain chute still visible. The premises were used as a brickyard after flour milling ceased. Demolished in 1978. 1950s
IMAGE LOCATION: (Warwickshire County Record Office)
Reference: PH, 734, img: 7334
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I frequently cycle along Haseley Mill Road.  Just past the farm buildings, if one is heading towards Haseley church, there is a field containing several small square brick-built structures.  They do not appear to have any function or openings.  Does anyone know what they are?