BROADWAY TOWER NUCLEAR BUNKER

Beacon Hill in Worcestershire has long been famous for the eccentric Broadway Tower built in 1799 by Sir William George the 6th Earl of Coventry but not many people know that just 180 metres to the north is the once secret Nuclear Observation Bunker used by the Royal Observer Corps between 1959 and September 1991.

THE OBSERVATION POSTS

During WWII the R.O.C. post at Broadway Tower was little more than a large pit dug into the ground and surrounded by sandbags. Spotters were always on watch for formations of planes, particularly those heading for the nearby industrial centre of Coventry.

In 1950 shortly after WWII a new above-ground observation post was constructed north of the tower. Made of precast concrete slabs, and little larger than a garden shed, it had two small rooms and a wooden roof covered with bitumen felt.  A phone line connected it to the regional control centre.  It has been partially restored but, at the time of writing, is still missing part of the roof that could be raised for observation purposes.

The Broadway Tower underground Nuclear Observation Bunker was constructed around 1959.  The ceiling of the structure is approximately 2.5 metres below the surface and the base reaches a depth of 7 metres.  Constructed from reinforced concrete it has its own ventilation ducts and was powered by special batteries in the event of mains electrical failure. There is no obvious lead-metal lining to make it fully radiation proof but would have still provide quite good protection against the initial gamma rays due as it was underground.

The rooms are accessed through a narrow vertical shaft that originates in a concrete bulkhead that extends approximately 70 cm above the ground.  This can be sealed by a metal hatch which appears insufficient to have protected the occupants from any serious nearby blast.

The ladder is basic and made of steel.

The observation post itself is both small and cramped and is comprised of two rooms - an operations centre and an adjacent toilet.  The operations room had two bunk beds, seats, a filing cupboard (alcove) and a control desk.  Metal sliders could seal off the ventilation ducts and various smaller pipes led to the surface to allow access for instruments to be used. The whole area was approximately 6m in length by 3m wide.

It was fitted with a range of equipment that was standard issue for all Nuclear Observation Bunkers (cells).  These were largely divided into two groups.

Equipment for the detection and grading of a nuclear blast included:

The standard BPI (Bomb Power Indicator) This generally looked like a large white pressure gauge and was connected to the surface by a hollow metal pipe. On the surface a pair of baffles provided the pressure change mechanism. As the blast wave from the nuclear explosion passed over the bunker the pressure change could be measured.  This result could then be compared to the distance-from-blast to calculate the kiloton yield of the nuclear explosion.  The device was designed by scientists at the Aldermaston atomic facility in Berkshire and tested for accuracy during real nuclear tests carried out on Christmas Island and at Maralinga in Australia.

The GZI (Ground Zero Indicator) was also sometimes known as The Shadowgraph.  A small metal drum was mounted on the surface above the bunker. Inside the drum were four pinhole cameras behind which were transparent grids and light sensitive paper.

Each camera was aligned to a point on the compass and the grid further specified both the precise location and the height.  the intense light of the blast would pass through the pinhole lens and burn a precise mark onto the paper.  An observer would then retrieve the paper and replace it with a new sheet. The combined blast pressure reading and grid reference burn mark would be communicated to the regional control centre.

Phone Reporting and Teletalk

Initially the R. O. C. staff were expected to report in their observations via above surface telephone lines.  It quickly became obvious that these would be highly vulnerable to both blast damage and EMP destruction.  By 1964 the Teletalk system had been introduced and would make use of evermore secure systems and subsurface telephone lines hardened against electromagnetic interference.

As it was expected that some of the posts would be destroyed in the initial attack they were linked together in clusters and had extra radio systems. Thus if a bunker recorded an atomic blast but had lost direct communications links the observation could be passed on to a fully operation bunker.

Equipment for the Measurement of Radiation included the RSM (Radiac Survey Metre number 2) was introduced as early as 1955 and was used to measure radiation levels. It required powerful 30 volt batteries to operate and used a GM tube to detect radiation. It was largely replaced by the FSM (Fixed survey Meter) which still required the powerful batteries but used an above ground ionisation detector located under a polycarbonate dome.  This was connected to the bunker via a coaxial cable. in 1982 with the PDRM82 (Portable Dose Rate Meter) which was significantly lighter, more sophisticated and needed only three 1.5 volt batteries.

SAFETY AND SURVIVAL

The R.O.C. Broadway Bunker volunteers took their work seriously and spent many hours in cramped and often cold conditions. Fortunately the cold war never turned hot and nuclear war was avoided.  There were times when the stations were put on high alert and it was the R.O.C. who realised how serious the treat truly was.  It must have been especially hard during the Cuban Missile crisis of 1962 when expectations of a global nuclear conflict peaked.  At other times it could be fun and many people involved recall a sense of strong camaraderie.   Although they were sealed in their bunkers not all observers were expected to survive an attack nor were the bunkers made for long-term occupation.

The bunkers would withstand a blast from a weapon similar to those used at the end of WWII only if they were more than 5 kilometres from ground Zero.  Once megaton weapons were available they needed to be more than 20 kilometres away.  Had the notorious Tsar Bombs (the AN602 hydrogen bomb) with a 50 megaton yield been used then that distance would have had to increase to nearly 40 kilometres.

In the event of a blast the bunker could sealed although observers were expected to venture outside to retrieve data from the GZI.  Decontamination facilities in the bunkers were limited or nonexistent. It was estimated that it would take two to three weeks before external radiation levels dropped sufficient  to allow limited outside exposure.  Even then the survivors would have emerged to a devastated landscape.  While food supplies were stored in the bunker they were limited and sever rationing would have been required.

RESTORATION

Today the Broadway Tower Observation Bunker has been extensively restored and was officially reopened on the 20th May 2011. It can be visited several times a year during the summer months. Much of the original equipment on display was supplied by the Flixton Museum and British Telecom. The facility is now considered one of the best examples of its type in the UK. It is now an almost perfect time capsule from 1991 when it was used for the last time. It is currently managed by the management of Broadway Tower and maintained by members of the ROC Association - North Cotswold branch.

ROYAL OBSERVER CORPS - BUNKERS

Essentially a civil defence organisation reporting to the RAF Strike Command it was made up of volunteers and started in 1925.  The purpose of the Royal Observer Corps was to identify potential enemy aircraft, their flight paths and possible intentions. Originally just 'The Observer Corps' they were awarded the title 'Royal' in 1941 as a mark of respect for their incredible efforts and achievements during the Battle of Britain. Their commitment and successes continued throughout WWII and became recognised as an essential part of the military infrastructure. Towards the end of the war they had a taste of their future role as they began to be used to spot guided missiles in the form of V1 Flying bombs and V2 Rockets although in the case of the latter it was usually after they had reached their target.

As the devastation of the atomic weapons used on Japan in 1945 became clear and conflict with Russia and its allies became a reality, a future use for the R.O.C. was devised.  After the success of a defence planning exercise in 1958, known as Nightbird, they would continue watching the skies but now on the lookout for soviet aircraft carrying nuclear weapons. As the cold war intensified and missiles became the real threat their role changed again.  The military command accepted that in the event of a nuclear strike at least some of the missiles would reach their designated targets.  It would be critical to know where the detonations had taken place and the size of the explosions.  In particular, it would be vital to know whether they were air burst or ground burst as this would seriously affect the amount of radioactive fallout that could be expected.

Tupolev Tu 160 'Blackjack' Atomic Bomber circa 1994 (Wikimedia Commons)

The Royal Observer Corps was fully disbanded in 1995 as the threat of an atomic war with the Soviet Union was by then consider so unlikely as not warrant the effort involved in maintaining the Nuclear Reporting Cells.  As a curious footnote it is worth noting that as recently as September 2008 a Russian nuclear bomber know as the Tupolev TU 160 'Blackjack' flew within 20 miles of Hull on the UK coast before being detected.  Even after it had been located it turned out that the RAF had insufficient jet aircraft to intercept it and remind the Russians that it was politically rude to fly so close to Britain.  Perhaps it's time to reinstate the R.O.C.  (The Mail Online - 30 September 2008)