Internal east portals of No2 tunnel. The concrete partition wall has been partly demolished but can still be made out in the centre of the photo. The room behind the partition housed the diesels (105 on the plan) and the  blocked-up portal (arrowed) led the exhausts to the outside. The room in the foreground contained the environmental coolers (106 on the plan) and the blocked-up portal on the centre left channelled the waste heat to the outside.

Photo: Jan West

Update: 23/06/2013

During 1977 the MoD decided to remove the diesel generator from the UGHQ. To achieve this the concrete partition, described above, had to be removed. Here we see Nigel Ostler-Harris (wearing red gloves) and Trevor Critchley using a hydraulic burster.

Photo: Nigel Ostler-Harris

Update: 23/06/2013

The Diesel generator set being inspected by Peter Griffiths the then MP for Portsmouth North. If you know anything about this type of engine then please contact me.

Photo: Nigel Ostler-Harris

It's a 6 cylinder Ruston & Hornsby engine. - Stoker Smith - 26/07/2013

Tunnel portal No3 (EE3 on the plan). The area around it is now heavily overgrown. The gate and entrance have both been replaced during the 1990s. The door frame is reinforced with 2 steel buttresses, and the gate is covered with 1 inch steel mesh. The adit survives because of the continued need for underground ventilation and emergency escape. This was used as an entrance to the NATO communication centre which made use of the underground complex during the Cold War. During the early morning the confidential waste was brought out here and burnt.

View through the gate of portal No 3 (EE3 on the plan). The lining closest to the portal has been sprayed with shotcrete, 

further back the steel colliery style ribbing is exposed. The adit turns sharply to the right leading to a blast trap, and the first set of blast doors.

There is a strong outflow of cold damp air all year round.

Further along the No3 tunnel is a fine example of a blast trap. The tunnel on the left leads off to the underground complex whilst the one on the right leads to a brick wall intended to reflect back any bomb blast. The hinges on the wall indicate that heavy blast doors were once fitted.

No3 tunnel showing a doorway on the centre left as it leads into UGHQ proper. Its height has been increased postwar by removing the upper 1 foot of reinforced concrete. The doorway is a 'pinch point' for a blast and gas proof sliding door. This door was 6 inches thick and its racer track can be seen on the floor.

Update: 25/04/2014

The circular patch on the floor shows where a large air intake fan was situated. Ducting has been located under the floor which runs to the outside of tunnel No 3. The photo below shows a large square hole in the top of the other side of the blast wall where the air flowed in.

Source: Andy Stevens (UCAP)

No3 tunnel again looking out from the UGHQ (106 on the plan) - opposite to the previous photo. The doorway and the alterations to it show up well. During the mid 1990s the complex was broken into, hence the graffiti on the wall. 

Photo: Nick Catford -  Subterranea Britannica 

Update: 23/06/2013

Nigel and Trevor at it again. This explains the reason for the heightening of the doorway in the above photograph. It was to enable the generator to be removed as described previously (above).

Photo: Nigel Ostler-Harris