Originally Posted by Always a Sapper
While not long or large tunnels the standard WW2 era JRC (like the one at Bicester or Azimghur Bks (ex RAF Colerne) had two Air Raid Shelters built into the basement, one at each end of the Bldg. The normal entrance is via a door at the bottom of the staircase at each end of the Bldg, stairs go down and then turn into the shelter. There is a escape tunnel at the opposite end which ran for about 50 mtrs to a vertical ladder going to a counter balanced hatch.
The escape tunnel hatches at Middle Wallop can be seen on GE between the NAAFI/Cookhouse and what was once the square.