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High on the ridge of Dollis Hill, North London, the Post Office Research Station was built in the late 1920's and early 1930's. This site, eventually 8 acres in extent, was where the main telephone company for Britain did research into the frontiers of electronics. It was the place that Tommy Flowers did the research and came up with the design for Colossus, the worlds first programable electronic computer, that was used at Bletchley Park to crack the most resistant German codes, produced by various types of encryption on teleprinter machines. It was a secure site and when the Government of the late 1930's was looking for somewhere to build various safe hiding paces for its important departments, in the event that central London was bombed and became uninhabitable for those departments, was one site where the government cast its gaze. This would be the site for one of its secure bunkers. This one was to be the retreat for the Cabinet Office, and specificaly the War Cabinet. 

As war approached, the plans were finalised and in 1939 construction began in the corner of the site next to Brook Road. A big hole was dug and various army type huts were put up to disguise the intention of the builders. Much of the work was done at night so that its purpose would not be too obvious. 15 months later in 1940, the bunker was complete. When the invasion threat was at its height, there was the intention to move most important government departments to the West of Britain and the local London citadels would have been by-passed altogether. The fall of France meant that even this move to the Midlands and West of England would leave them in range of German bombers. All the options would be kept open, but it looked likely the dispersed London sites would be used. The bunker under Dollis Hill was thought to be able to withstand a direct hit from a heavy German bomb when built. It was no match for the later rocket assisted armour piercing bombs and the nuclear weaponry when it arrived. It had an above ground building and the bunker itself was on two levels below the ground. The upper and larger level is protected by a five foot thick reinforced concrete roof. Between the upper level and the lower level is a three foot thick concrete layer. The building was made to be sealed off as necessary and had its own generator and air filtration plant built it. This is a small and unsophisticated bunker compared with the later nuclear bunkers, but it was not made to face the same threats. 

Churchill did come here a few times and he chaired one cabinet meeting here, but he did not like the place, decribing it as "Far from the light of day". He also brought his wife and son here on a visit. Two flats (18 and 27) in Neville's Court at the end of Brook Road were converted to one for his use, but he possibly never stayed there. This place was secret when built and was locked up in 1943 and left, after the furniture and contents were moved to another site, the Rotundas in Marsham Street, code named ANSON. The Post Office workers used parts of the upper floor for a social club in the 1960's and also for storage, but nothing much else was done with it and it was sold off with the rest of the site after the Post Office moved away to Martlesham in the early 1970's. In 1997 the above ground building was demolished and houses built on that part of the site. Two entrances were preserved and as part of the owners agreement for purchase of the site, the bunker is going to be opened to the public at least 2 days per year. It has been drained of water and made safe with some new lighting and a lot of clearing up the debris from the floors, but it is otherwise as left, empty but interesting!

 
Picture by Frank Milne