LONDON.- A letter making clear Prime Minister Winston Churchill’s verdict on the underground rooms selected as his wartime bunker will go on show for the first time in a new display marking the 70th anniversary of the start of the Second World War. Undercover: Life in Churchill’s Bunker opens on 27 August 2009 and runs until 27 August 2010 at the Churchill Museum and Cabinet War Rooms in central London.

The letter - on loan to the exhibition from The National Archives - was written by Patrick Duff (Permanent Secretary at the Office of Works) to Sir Edward Bridges (Secretary to the Cabinet). It recounts a meeting between Duff and Churchill held on the morning of 13 September 1940, during which the pair discussed the site from which Churchill and his War Cabinet were directing operations. Churchill was clearly angry at discovering that the site was not bombproof, claiming that Duff had ‘sold him a pup’ and ‘letting him think that this place is a real bomb-proof shelter’. Duff confessed that he was ‘indignant’ at being accused by Churchill of misrepresenting the safety of the site.

Later in September 1940, a bomb narrowly missed the War Rooms building, making a crater near the Clive Steps at its northwest corner and on 14 October bombs struck both the Treasury and Horse Guards Parade, causing blast damage to the kitchen, pantry and offices on the Treasury side of 10 Downing Street. Shortly after this, Churchill authorised the strengthening of the War Rooms, with a large concrete slab being built over part of the site. Churchill took personal interest in this work, offering advice to the workmen on bricklaying, a favourite hobby of his. The slab made the site much safer, but still it would not have been a match for the larger bombs at the end of the war.

Phil Reed, Director of the Churchill Museum and Cabinet War Rooms, said ‘Since the Cabinet War Rooms opened to the public twenty-five years ago, there has been plenty of debate about how secure they were and whether they would have survived a direct hit during the Blitz. Certainly, several War Room veterans were unaware that the site was vulnerable throughout their period of service underground. This letter makes clear Churchill’s surprise and indignation at being handed a potentially vulnerable bunker’.

Cressida Finch, exhibition curator, Churchill Museum and Cabinet War Rooms, said ‘This whole episode tells us a lot about Churchill's personal bravery. Although he was angry on learning that the War Rooms were not brilliantly safe, he was determined not to leave central London and be seen as abandoning Londoners. Also, there is a direct comparison with Hitler, whose bunker in Berlin was 33 ft deep. Churchill’s War Rooms, (in effect a basement rather than a bunker) are only 10ft below ground. The contrast says a lot about the two men’.

In an interview for the new exhibition, Ray Smith, a clerk in the Joint Planning Committee, based in the War Rooms, said ‘The combination wasn’t really bomb proof; it was only about ten feet lower than the underground at the St James’s Park. Although it was protected by the building above, a bomb falling from the park at an angle would probably have penetrated through the soft earth outside and into the War Rooms. The rooms above were filled with concrete, which was quite a major operation. They had big cement mixers, pumping it through with a big pump. They also used the tramlines being taken up from London at the time to use for the reinforcing rods. When the war started, they were talking about having protection against 500lb semi- armour piercing bombs. As part of the improvements, the quadrangles within the building were filled with scaffold piping at roof level, and anti-torpedo type net hung across to catch any landmines or parachute mines coming down. So a lot of work was done after the war started, to protect (and) improve the protection that was given.’

War Room typist, Joy Hunter, said ’When we were in the war rooms, thinking about the bombing and the buzz bombs and so on, I always felt completely safe, absolutely. It never occurred to me that the building could come down on top of us.’

Undercover: Life in Churchill’s Bunker draws on new personal accounts to build a picture of daily life beneath the London streets, where events of the War were being shaped and world-changing decisions made. Stories, historic images, previously unseen personal objects and the voices of War Room veterans combine to create the tense but often humorous atmosphere in the series of rooms selected as the secret war headquarters for Churchill and his War Cabinet. While the personality of Churchill looms large throughout, many uncelebrated characters are also brought to the fore, many of them secretaries or typists leading seemingly ordinary lives but involved in an extraordinary event.

The Cabinet War Rooms were created in 1938, as the underground storage areas of the Office of Works Building in Whitehall were converted to house the central core of government and to become a military information centre, serving the Prime Minister and the Chiefs of Staff of the air, naval and land forces. Intended as a temporary site, the rooms became operational on 27 August 1939, a week before the German invasion of Poland and Britain's declaration of war. This 'temporary' but timely measure served as the central shelter for government and military strategists for the next six years.