THREAD: Spent 3 days @shorehamfort excavating a keyhole-shaped structure outlined in brick. We thought this might have been an emplacement for a WW2 anti-aircraft light machine gun (AA LMG). Stage 1 was to brush off and expose the remains breaking the surface. #ww2Sussex 1/8 
Compacted shingle was trowelled off to reveal cinders beneath. Below this was a concrete floor, yet the rear of the structure suggested a sunken entrance. We also had what seemed to be a holdfast with a ring of 1-inch bolts - far too substantial for our AA LMG theory. 2/8
Late on day 2, we decided to put a sondage through the floor to see if the structure went below ground, as nothing was making sense. Breaking through the concrete we realised what we initially thought was the floor was actually a postwar capping to reinstate the track! 3/8
We had 1 day left; slow progress was made through the concrete and rubble backfill, but we eventually found the original floor 70cm below ground. We also found green camouflage paint on some of the loose bricks! The 'holdfast' also began to reveal its true nature... 4/8
The structure was beginning to look like a Spigot Mortar (aka 'Blacker Bombard') emplacement, although some questions remained. The trench was extended along the entrance wall, but revealed no evidence of steps. The structure was cleaned and recorded. 5/8
Photos taken from the 5-metre selfie stick show the form of the structure; neither the pit or the pedestal are truly circular! We ran out of time, but got enough data to confirm a Spigot Mortar emplacement. 6/8
Comparing our data to manuals, the dimensions are broadly similar. The 'holdfast bolts' seem to be pedestal rebar so the standard 'birdcage' was not used here, making this a local adaption of the design. No ammo lockers were found, but some may exist in the unexcavated part. 7/8
We backfilled the trench; our report will mean that this important structure can be added to the Historic Environment Record (HER). Thanks to @shorehamfort for their hospitality! 8/8
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