Site Records

Site Name: Station Z - Air Ministry Citadel

In the grounds of Kodak Ltd.
Headstone Drive

OS Grid Ref: TQ148898

Sub Brit site visit 3rd November 2005

[Source: Nick Catford]

In addition there is a direct tie line from Richmond Terrace to Z on the 'black' tie line system

A small Insurance Party is in permanent occupation of the citadel. Apart from police and guards the sections actually manned and operating are: War Room, Telephone Exchange,
Teleprinter and Communications

The Air Ministry citadel is ready for immediate occupation. Rooms have been furnished and allocated to staff, telephone and teleprinters have been installed and telephone directories prepared. The war room records are maintained up to date and domestic services are arranged."

Another National Archive file (Air 20/2893) relates to the Locations of the Air Intelligence branch. AI 1 (Intelligence Civil Clerical Staff Administrative Section) goes part to Whitehall and part to Harrow and AI 1 (A) Intelligence RAF Staff Administrative Section go to Harrow

Photo:The upper floor (basement) at Station Z. The ventilation trunking suspended from the ceiling is a recent addition.
Photo by Nick Catford

Other departments relocating to Harrow include: AI 1 (G) Technical Intelligence & Crashed Enemy Aircraft examination section. (HQ is at Harrow with a regional organisation covering the rest of the UK, Northern Ireland and the Middle East.), AI 1S Security Section, AI 1 T Translation Section and ADI Supply of maps to the RAF.

After WW2 the Air Ministry continued to occupy 28 office sites in UK, notably in London these included the steel framed building at the Marsham Street rotunda site. Station Z still housed some Air Ministry departments and was still earmarked as a wartime dispersal for administration staff until 1955.

By 1955 some of the Air Ministry's accommodation problems had been resolved and the building was vacated by peacetime staff although the site remained available as possible wartime office accommodation although this may not have included the bunker.

In 1955 the Home Office Directorate of Telecommunications moved into the surface offices which became their headquarters for the maintenance of the Home Office radio network for civil defence, the police and the fire service. It also ran the Hilltop Radio system (as detailed by Duncan Campbell in War Plan UK). For this service large steel lattice radio mast was erected in the courtyard. It was also the regional depot for Civil Defence Region 5 until that was divided up in late 1950's.

1950's communications mast for Home Office Radio Network
Photo by
Dr. James Fox/John Harris from RAF Holmpton archive

In 1966 the underground accommodation was designated as a short term location for Sub Regional Control 6.2 covering Berkshire, Buckinghamshire, north and west London. The longer term plan was to upgrade the old RSG at Warren Row. By 1971 this function had disappeared following the reduction in planned SRC's and the disbanding of Civil Defence in 1968. No work had been carried out at the site in connection with this proposed use.

Lower floor plan
Drawn by
Nick Catford

By 1980 it once again acted as the Region 5 radio depot, as that region had been reformed in 1971. This function was retained until c.1992 when the site was vacated by Home Office. It then became a store for the adjoining HMSO print works.

Once the HMSO works closed, Kodak brought the site for expansion of their large adjoining complex and the surface office block was demolished in 1996.

Access to the bunker was maintained via one of the emergency exits but the bunker was allowed to flood. Until recently, the sub-basement was flooded to a depth of several feet but the water has now been pumped out with only a little standing water remaining. The pumps are still in place to ensure that the flooding does not reoccur and new ventilation trunking has been installed to ensure a supply of fresh air throughout the bunker. Kodak has no planned use for the site.

Photo:The inner courtyard in c.1985. The bunker is beneath the courtyard and the building that surrounds it. Note the two ventilation towers. The radio mast was erected in 1955 for the Home Office Hilltop Radio system.
Photo by Dr. James Fox/John Harris from RAF Holmpton archive

The thee storey surface building has been demolished; the only indications of anything below ground are a small prefabricated metal entrance hut over the top of the northern emergency staircase, two ventilator outlets with an emergency escape hatch between (this was formerly the plant access point) and the concrete caps of the lift shaft and the other emergency exit.

The upper basement level has been stripped of all original fixtures and fittings including all internal partition walls leaving one large 'open plan' room with 25 supporting pillars evenly spaced in five lines. On the east side the original plant entrance, loading bay and east stairway are enclosed within a walled area. The stairs have been removed and the main plant access hatch has been slabbed over but a personnel access hatch has been retained and there is a wooden ladder against the wall if access is required, this now acts as an emergency exit from the bunker. Originally there would have been heavy blast doors at all entrance and exit points but these have also been removed although the 8" thick steel door frames are still in place to indicate their position and size. The basement was originally served by a lift from the upper floors, the lift shaft is still there but the lift and all the lift machinery has been removed.

Photo:The ventilation plant area in 1985
Photo by Dr. James Fox/John Harris from RAF Holmpton archive

Photo:The ventilation plant area in 2005. The machine bed in the 1985 picture is on the right in the 2005 picture.
Photo by Nick Catford

There are four stairways down to the protected lower level or sub-basement. Two of these are wide concrete stairways with door frames at the bottom where the blast doors have been removed. There were originally two spiral staircases which acted as the emergency exits; narrow blast doors at the bottom giving access to the sub-basement. One of these spirals has now been removed and the adjacent stairs up to the surface have been blocked at ground level. The other spiral, at the bottom of the present access stairs, is blocked off and out of use. On the west stairway there are two rails mounted on the steps, these were used for moving a wheeled cart between levels. The cart can still be found in the upper basement, it is unclear if this is an original feature or was added post war.

The sub basement is similar to the basement with 25 pillars directly beneath those in the basement. Again all internal partition walls have been removed with the exception of a small block extending into the room from the east wall. Here there is one separate room and an adjacent short corridor leading to the east stairs. A number of concrete plinths in the north east corner indicated where the ventilation plant was sited. The standby generator was in the corridor leading to the emergency exit stairs on the north side of the bunker, adjacent to the existing spiral stairs. Although the generator has gone the substantial concrete engine bed is still there.


  • Bob Jenner
  • Keith Ward
  • Ken Valentine (Willesden at War Volume 2) ISBN 0 9514258 6 2
  • National Archive files: Air 19/190 & Air 20/2893

Thanks to Kodak Ltd. for allowing access to the site

For further pictures of Station Z click here

[Source: Nick Catford]

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Last updated: 04 01 2011
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