Old_ROF. Going by what looks like a sea wall in the distance, it looks more likely it's Eskmeals, but it's hard to tell. It doesn't looks like any of the sea firing points at Shoeburyness though, the seawalls were far more robust in general.
I remember the EXP38 designation, but as I was only doing the instrumentation, photography and radiography, I didn't often get mixed up with the weapon designations, design, etc, I was too busy rushing around. From what I remember, the guns used in the trials were either dropping block or interupted screw breechs designs. The ammo two-peice with the rear module using a steel stub case. Barrels were either smoothly tapered with no extenal features, or machined for a fume extractor and/or a muzzlebrake/muzzle referencing system. The smooth tapered barrel was used with the interupted screw breech. On the machined version, there were no fume extractor ports, just the external machining to fit the extractor.
We did use the EXP45 a few times too... an interesting beast!
I now work for Jane's, so I can look through what records we have here on the history of the program(s). A quick scoot over the reference data (not news) gives these 140 mm programs.
140 mm Future Tank Main Armament (FTMA)
140 mm Advanced Tank Cannon (ATAC) System
Future NATO 140 mm tank gun
Israel Military Industries 140 mm smoothbore gun
Rheinmetall 140 mm smoothbore gun
RUAG Land Systems 140 mm tank gun
SSTC ARA 140 mm smoothbore tank gun Bagira