'John'

This post's title relates to a 4" BL static Gun mounted at Thorpness, one of four that arrived in Suffolk in the summer of 1940 - three mounted in a static role (nicknamed 'John', 'Luke' and 'St Peter'), the forth one apparently mounted on a ship in the RN training establishment at Shottley (but still manned by field gunners!).

The 55th Div War Diary describes how one evening, RA Eastern Command announced to CRA 55th Div that four 4" naval guns and wooden baulks to mount them on would shortly arrive by rail. Each gun weighed 25 cwt, the cradle and pedestal 48 cwt and each of the two wooden baulks 24 cwt. The War Diary notes that 55th Div Artillery had no equipment at all to deal with these sort of weights. The problem of getting them into position was solved in the end by enlisting the help a party of naval ratings under the command of Lt Scotland RN who were mounting coastal defence artillery in 55th Div area, a R.A.O.C recovery crane and a liberal amount of manpower. The guns were initially manned by 87 Field Regt and later 59th Med Regt. 

The structure in the photos and plan below matches the given position for the gun mounted at Thorpeness. 164th Brigade War Diary gives its task as observed fire north and east and indeed the two 'open embrasures' are indeed facing north and east. I am unsure if the structure originally had any over head cover - certainly no indication on the main walls of supporting any overhead structure,  but there are pillars that would have supported something. The purpose of the huge bent RSJ is a complete mystery! Finally, observed fire to the east can only have been for anti-ship / barge - was the gun supported with a fighting light?
Image 1: Plan of structure
Image 2: South side of structure with blast wall entrance
Image 3: 'Open Embrasure' facing east - note pillar in shrub in background.
Image 4: RSJ - purpose unknown!
Image 5: Looking into the structure from the east facing 'open embrasure'