The son of a bricklayer, Flowers served an apprenticeship at the Royal Arsenal, Woolwich. While there he obtained an electrical engineering degree from the University of London. He then joined the Post Office as an electrical engineer at their Dollis Hill research station, where he explored the use of electronics for telephone exchanges. In 1942 he was appointed to work with Alan Turing to build a decoder for the relay-based Bombe machine that Turing had developed to help decrypt Enigma codes. Although the decoder project was abandoned, Turing was impressed with Flowers' work, and in February 1943 they began working on developing an automated decoding system for Lorenz cyphers. After initial work with a machine called Heath Robinson, Flowers proposed an electronic system (called Colossus), which was successful and had a major influence on the war’s proceedings. Post-war he became the Post Office’s chief engineer and also worked with the National Physical Laboratory in computer development. His vital work at Bletchley Park was not fully appreciated until many years after the end of the war.
The organisational arrangements at Bletchley Park reflected the British approach in successfully harnessing brilliant minds to support the war effort. Turing, Welchman, and their colleagues had the ideas, but they needed sympathetic minders such as Commanders Dennison and Travis, both RN, to make their work effective and to provide the organisational framework. It is doubtful whether anything similar occurred anywhere in Germany during the war.
Y-Service
Operating out of some 30 separate stations, personnel from the Royal Signals and other agencies listened into German wireless traffic; later from stations in India and elsewhere in the Far East, they listened into Japanese signals. Many amateur (‘ham’) radio operators supported the work of the ‘Y’ stations, being enrolled as ‘Voluntary Interceptors’. Much of the traffic intercepted by these stations was recorded by hand and sent to Bletchley Park on paper by motorcycle couriers or, subsequently, by teleprinter over Post Office landlines. A large house called Arkley View on the outskirts of Barnet acted as a data collection centre at which traffic was collated and passed to Bletchley Park. It also acted as a ‘Y’ station.
In addition to wireless interception, specially constructed ‘Y’ stations also undertook High Frequency Direction Finding (HF/DF, known colloquially as ‘Huff Duff’) on enemy wireless transmissions. This became particularly important in the Battle of the Atlantic (1939–1945), where locating the positions of U-boats became a critical issue. Admiral Dönitz told his commanders that they could not be located if they limited their wireless transmissions to under 30 seconds, but skilled HF/DF operators were able to locate the origin of their signals in as little as six seconds.
The land-based DF stations preferred by the Allies operated on the Adcock antennae system, which consisted of a small central operators’ hut surrounded by four 10-metre-tall aerial poles, usually placed at the four compass points. Aerial feeders ran underground and came up in the centre of the hut; these were connected to a direction-finding goniometer and a wireless receiver that allowed the bearing of the signal source to be measured. In the UK some operators were in underground metal tanks. These stations were usually located in remote places, often in the middle of fields. Traces of Second World War D/F stations can be seen as circles in the fields surrounding the village of Goonhavern in Cornwall.
Far Eastern Codes
The Japanese had different coding systems for diplomatic, naval, and army messages. Also, after a message had been decoded, it had to be translated before it could be read by most English-speaking officials. Some signals intercepted by British listening stations were sent to the UK for GC&CS cryptologists to attempt to decipher, and in 1939 John Tiltman managed to decode the then-current Japanese naval code.
Before Pearl Harbour, American, British, Australian, and Dutch cryptanalysts were listening to and trying to decode Japanese naval and other signals. The British office was originally in Hong Kong but then moved to Singapore; Colombo (in Ceylon, now Sri Lanka); and Mombasa, Kenya. Wireless reception there was particularly poor, and in 1943 it returned to Colombo. Following the Japanese invasion of Malaya, Army and RAF decoders were based in Delhi, India.
The principal Japanese encoding system for diplomatic messages was called Purple by American cryptanalysts, while their decoding work was known as Magic. American and British officials had managed to decode some signals before Pearl Harbour. Later they were able to decipher most Japanese messages. The Russians also succeeded in breaking into the Purple system in late 1941; the messages revealing that Japan was only going to attack the US and UK territories allowed Joseph Stalin to move considerable forces from the Far East just in time to help stop the final German push to Moscow.
Covert Communication Centres
Military establishments and training centres of all kinds were established throughout the United Kingdom, and many isolated country houses were taken over and adapted for specific purposes – not only Bletchley Park, but also Beaulieu in Hampshire and Arisaig House in Invernessshire for the training of Special Operations Executive (SOE) operatives.
Communications with forces operating overseas and Allied governments were either by radio or submarine cable. There were major pre-war radio transmitting stations at sites such as the beam wireless transmitter at Dorchester, Dorset; the very low frequency transmitter at Rugby, Warwickshire; and the wartime reserve station at Criggion, Powys. With their masts up to 250 metres in height they were impossible to conceal.
On the other hand, major efforts were made to conceal the activities taking place in the many villages and houses throughout Britain where covert communication centres were sited. One was at Porthcurno, a small coastal village near Land’s End in Cornwall, which as early as 1870 had been chosen as the British terminal for the first submarine cable. By the outbreak of the Second World War it operated as many as 14 cables and was able to receive and transmit up to two million words a day – for a time it was the largest submarine cable station in the world. Situated some 150 km from Brest, it was considered to be extremely vulnerable following the fall of France, and elaborate measures were taken to protect the station’s equipment. Local tin miners were engaged in June 1940 to dig two parallel tunnels, and two smaller cross-tunnels, in the granite headland behind the station. This was completed within 12 months, and the receiving and transmitting equipment was then moved into the main tunnels. The entrances, emergency exits, and operatives’ housing were all camouflaged to blend in with the local topography. The station was closed in the 1970s and is now a museum
Another was at Heighton Hill, just north of Newhaven, East Sussex, and known as HMS Forward. In 1941 a labyrinth of tunnels was constructed in the chalk of the South Downs to house facilities for a Royal Naval headquarters. These were demolished at the end of the war, and virtually nothing was known about HMS Forward until Geoffrey Ellis – a Post Office engineer who as a local boy had seen it being built and was intrigued to know what had taken place there – investigated it in his retirement. His researches established that there had been two telephone exchanges, ten teleprinters, two Typex machines, a wireless telegraphy office with 11 radios, and a voice-frequency telegraph terminal for 36 channels. The tunnels housed a standby generator, an air conditioning system with gas filters, a galley, toilets, cabins for split shifts, and the recently invented phenomenon of ‘daylight’ fluorescent lighting. The complex was equipped for every contingency from failure of the public utilities to direct enemy action. Ten coastal radar stations along the Sussex coast reported directly to HMS Forward every 20 minutes. All their information was filtered and plotted before being relayed by teleprinter to similar plots at Dover and Portsmouth. The HMS Forward plot maintained a comprehensive maritime surveillance of everything that moved on, under, or over the English Channel from Dungeness to Selsey Bill. Further intelligence was obtained from military airfields by private telephone lines. For operational security reasons, each plot understudied its neighbour, with
