During WW2 a secure underground radio station was installed in tunnels excavated in the face of the Paulsgrove Chalk Quarry a short distance to the south of Fort Southwick. This was linked to the combined underground headquarters located in tunnels beneath the fort. The radio station was located some distance from the fort as the highly visible aerial arrays would have provided an easy target.
The tunnels are still accessible although following post war quarrying, the two adits are now 40 feet above the quarry floor and can only be entered by climbing a scree slope (very slippery when wet). A narrow path joins the two tunnel entrances and between them there is a 12 foot by 8 foot unlined chamber cut into the chalk, its purpose is unknown although it is undoubtedly linked to the radio station.
The west entrance is 9 feet wide and 6 feet high with a rebate cut into the chalk face for a secure door. Once inside the entrance the unlined tunnel narrows to 5 feet wide by 6 feet high and runs northwards with a concrete sill running the length of the left hand side of the floor. A short distance inside the entrance there is a side tunnel 8 feet wide by 8 feet height and 21 feet in length. The tunnel is arched in section and lined with corrugated metal sheeting.
After 80 feet the main tunnels turns to the right through 90 degrees running east for 9 feet, initially this too is unlined but the last 5 feet are lined with corrugated metal sheeting. The tunnel then opens into a lined chamber 8 feet wide by 8 feet high and 17 feet in length. It has a concrete floor with a small pit on the north side with a 6 inch pipe terminating.
At the end of the chamber, there is an unlined stairway (10 stairs) dropping down 7 feet to another chamber which is 10 feet high, 8 feet wide and 42 feet long. Initially this is unlined but the last third is lined with corrugated metal sheeting. Sections of metal sheet lie on the floor suggesting that the chamber was originally lined throughout. There is some evidence of electrical fittings. On the north side there is a roughly cut alcove in the wall with a 6 inch borehole up to the surface.
At the end of the chamber the tunnel continues for a further 9 feet narrowing down to 5 feet wide by 6 feet high. It then turns to the right by 90 degrees running 62 feet out to the east adit in the quarry face. At the corner there is a second 6 inch borehole with a 1inch steel pipe running up to the surface. This tunnel is unlined with concrete sills on both sides of the floor and at the entrance, there is a rebate cut into the quarry face for a secure door. The tunnel is partially backfilled with chalk rubble.
On the cliff top overlooking the quarry there are some footings from a small brick building. There were at least four radio masts in the area, three to the west of the brick building and one to the east. Each mast was guyed at four anchor points, with 55 feet between adjacent anchors. Ten anchor points can be found and immediately above the radio station there is a short length of armoured cable sticking out of the ground.