Night Raid

by Taylor Downing

  In August 1934 he wrote a letter to The Times opposing the official policy on air defence. He objected to the fact that ‘it seemed to be taken for granted on all sides that there is, and can be, no defence against bombing aeroplanes.’ Claiming that it was inexcusable to accept such a defeatist attitude ‘until it has definitely been shown that all the resources of science and invention have been exhausted’,6 Lindemann laid down a gauntlet to the scientific community of Britain to come up with a way to identify an approaching fleet of enemy bombers in order to be able to direct the nation’s defences against such an attack.

  At the same time the man who would become Lindemann’s biggest rival entered the fray. Sir Henry Tizard was one of the most dynamic figures of British science between the wars. A tall man with a commanding nature, he got on with almost everyone despite his rather stern appearance, with a pointed chin, a moustache and spectacles. He was a chemist by training who had worked in Germany prior to the First World War in one of the pioneering centres of research under the supervision of Professor Walter Nernst. In the war he had been in the Royal Flying Corps, had learnt to fly and was put in charge of scientific research into aircraft and armaments at Martlesham Heath in Suffolk.

  After the war, Tizard moved sideways, away from pure research, to try to find ways of applying scientific advances to practical problems. He began to work on various government committees and soon earned a reputation as a fine chairman who was skilled in asking the right questions and in finding the right way to go forward. As secretary of the Department of Scientific and Industrial Research and chairman of the Aeronautical Research Committee, he met with many of the leading figures in government. In 1929 he was appointed Rector of Imperial College, London, and from this leading academic position he soon got to know all the leading university research establishments. So, with good contacts in both government and academia, Tizard was in a position to take a central role in co-ordinating scientific developments within the country.

  In 1934, like Lindemann, Tizard began to be concerned about predictions that bombers could inflict a devastating attack upon Britain. He wanted to make fighter aircraft and anti-aircraft defences more effective against an air attack. He concluded that the best way would be to seek some form of early warning of an approaching bombing fleet out over the sea before it reached British shores.

  Within the corridors of the Air Ministry in Whitehall an official decided it was time to act. A.P. Rowe was a typical civil servant of his day. He was a short man who wore round spectacles, smoked a pipe and had a mind that longed for order and organisation in a sometimes messy and confused world. He worked in a branch of the Air Ministry that dealt with scientific research, and during a quiet spell of work he called up all the papers he could find on the air defence of Britain. There were fifty-three relevant documents and Rowe studied them all. Realising that the nation’s scientists had contributed nothing to the development of technology for aerial defence, Rowe did what a good civil servant should do in such a situation. He wrote a memo to his boss, Henry Wimperis, the director of the Air Ministry’s scientific research section, pointing out that unless something was done to rectify the situation, Britain was likely to lose the next war.7

  Henry Tizard discussed his own thoughts separately with Wimperis, who had by now received Rowe’s memo. Together they resolved to form a committee ‘to consider how far recent advances in scientific and technical knowledge can be used to strengthen the present methods of defence against hostile aircraft’.8 The committee was duly formed, with Tizard as its chairman and two distinguished professors with experience of the armed forces, Patrick Blackett and A.V. Hill, as members. Blackett, a physicist at Birkbeck College, London, had been an engineering officer in the Royal Navy in the First World War and had taken part in the great naval battle at Jutland in 1916. He worked with Ernest Rutherford’s famous nuclear research team at Cambridge and had already completed the work that would win him a Nobel Prize after the war. He was in his late thirties and became an energetic member of the new committee. A.V. Hill was an older man who had been an artillery officer in the Great War, and had already won a Nobel Prize as a physiologist at Cambridge. Wimperis also joined the committee to represent the Air Ministry, and the bespectacled Rowe became its secretary.

  While this team was being recruited, Wimperis had a conversation with another luminary in the world of British science. Robert Alexander Watson-Watt was a short, round-faced and slightly chubby Scotsman. He ran the Radio Research Station of the National Physical Laboratory, based at Ditton Park near the Berkshire town of Slough. Watson-Watt had served in the Great War at the Royal Aircraft Establishment in Farnborough detecting the approach of thunderstorms, which offered a serious threat to the fragile biplanes of the day. Having designed a basic radio direction-finder to establish when storms were approaching, he continued to develop and improve this after the war, when sealed cathode ray tubes first became available. Having constructed a simple device to locate the existence of thunderstorms, he went on to explore other atmospherics that might threaten aircraft in flight. His Radio Research Station became a centre of expertise in direction finding using cathode ray tubes and in studying the atmosphere using radio waves. Watson-Watt was a lively, enthusiastic man, a great chatterbox with the ability to out-talk anyone. ‘He never said in one word what could be said in a thousand,’ wrote one of his colleagues later.9 Partly due to his verbosity, partly to his humble Scottish background and partly to the rarefied nature of his research, the widely respected Watson-Watt was still something of an outsider to the English scientific establishment.

  On 18 January 1935, Wimperis met Watson-Watt to discuss a phenomenon that had attracted much interest without so far yielding any real science. Inventors kept pestering the Air Ministry with proposals for a death ray that could be used to shoot down an aircraft, or at least kill a pilot at some distance. In bizarre consequence, the Ministry had publicly offered a reward of £1000 for anyone who could come up with a death ray gun that could kill a sheep at a hundred yards. Wimperis asked Watson-Watt if it would ever be a scientific possibility to kill a man at a reasonable range with a ray gun. Watson-Watt said he thought it highly unlikely but that he would investigate.

  Watson-Watt asked his junior colleague back at Slough, Arnold Wilkins, to calculate the force that would be necessary to boil a man’s blood at a distance of three miles. Wilkins was easily able to show that the immense amount of force that would be needed was far beyond any technology of the day. Watson-Watt responded by saying, ‘Well, if the death ray is not possible how can we help them?’

  Wilkins thought for a moment and remembered an observation he had recently heard from Post Office engineers who were in charge of short wave communications, that when an aircraft passed their transmitters they picked up interference on their receivers. The two scientists speculated that it might be possible to use this as a way of detecting an approaching aircraft. Wilkins again went off to do the mathematics and came back with the daunting conclusion that the energy returned from a radio wave that had hit a metal object and bounced back was likely to be less than a million, million, millionth part of that sent out; in mathematical terms 10–19 of that transmitted.10 Whether it was feasible to measure such a tiny amount would entirely depend on the power of the transmitter and the sensitivity of the receiver.

  Watson-Watt reported back to Wimperis that calculations showed that a death ray was impossible but that ‘attention is being turned to the still difficult but less unpromising problem of radio-detection as opposed to radio-destruction’. His note appeared just before the inaugural meeting of Tizard’s new Committee for the Scientific Survey of Air Defence on 28 January 1935. After considering various other options such as the deployment of barrage balloons, the use of infra-red, the deployment of toxic gases to harm an aircraft’s crew, and the construction of huge 200-foot ‘sound mirrors’ to hear the approach of enemy aircraft, the gentlemen of the committee seized upon Watson-Watt’s suggestion and asked f
or more details.

  Accordingly, Watson-Watt and Wilkins carried out a more detailed study of the possibilities. To their enormous relief, it seemed that with the very latest technology a radio wave with a length of 50 cm should produce a detectable echo of an object flying at a height of 20,000 feet at 10 miles distance. In a state of great excitement, Watson-Watt hurriedly wrote a memo, ‘Detection of Aircraft by Radio Methods’. He argued that by using the latest radio pulse generators and the most sophisticated cathode ray displays, it should be possible to calculate the length of time between the transmission of a radio wave and the reception of its return echo. As radio waves moved at the speed of light, roughly 186,000 miles per second, in one microsecond a wave would have travelled 0.186 of a mile or 328 yards. An echo received ten microseconds after being sent would have travelled 3280 yards, or nearly two miles. The metal object from which it bounced back would therefore be located at half this distance, as the radio wave had to travel there and back. In other words it would be one mile away.

  Watson-Watt concluded that the calculations were quite favourable, but that ‘I am still nervous as to whether we have not got a power of ten wrong but even that would not be fatal’ with the current state of technology. He pointed out that any detection scheme would have to incorporate a way of distinguishing between friendly and enemy aircraft and that it would be better to use shorter wavelengths, which were less vulnerable to atmospheric interference. He even wrote that it would be important to add height and bearing as well as range to the measurements. In only four typed pages, Watson-Watt laid out in this historic memo most of the principles of what would come to be called radar.11

  When the Tizard committee met for its next session, its members could barely believe their luck. They had been assigned one of the toughest defence problems of the day and here, almost at the beginning of their deliberations, the solution seemed to have dropped into their lap. Tizard invited Watson-Watt for lunch at his club, the fashionable Athenaeum, and was suitably impressed. He agreed to pass the memo on to the head of research and development in the Royal Air Force, Air Marshal Sir Hugh Dowding. A stiff, prickly man whose nickname within the RAF was ‘Stuffy’, Dowding, despite his reputation, was also outward looking and interested in new ideas as long as they were practical and delivered results. As desperately concerned about air defence as anyone else, he was keen to find a solution. He would go on to lead Fighter Command in the summer of 1940 when the results of this experimentation would be put to a critical test. But at this point, Dowding was still sceptical of new theories. He wanted proof that the concept was no more hare-brained than some of the other ideas that crossed his desk and he wanted a demonstration to see if the complex calculations that meant little to him on paper had any substance.

  So it was that on 26 February, Watson-Watt and Wilkins found themselves in the Northamptonshire field staring into a cathode ray tube. It had not been possible to quickly find a way of generating powerful enough radio waves and so the scientists ‘borrowed’ the waves that were being sent out by the BBC from their transmitter at Daventry. The RAF agreed to provide the Heyford bomber for the experiment and the pilot, who knew nothing of what was happening below, was told simply to fly a course up and down past the transmitter four times. Accompanying Wilkins was a handyman from the Radio Research Station named Dyer, who helped to construct the equipment needed for the experiment. And along with Watson-Watt, who drove out from London in his prized Daimler, came A.P. Rowe to observe and report back to Tizard’s committee.

  After this successful experiment, things began to move at high speed, reflecting the urgency that was widely felt in the need to establish some form of air defence. Dowding was sufficiently impressed to commit £10,000 to further development – a sum large enough in 1935 to fund a full year of staff and equipment costs. A new unit was set up to report to the Air Ministry with a small team of four scientists seconded from the Radio Research Station. Watson-Watt selected a remote strip of land on the extreme east coast of Suffolk called Orford Ness as a location for the intense phase of testing and development that was now called for. The shingle and marshes that made up this promontory, often wrongly referred to as an island, had been a test site in the First World War, and the RAF still owned the land and used it as an experimental centre. It was an extraordinary and isolated coastal strip only accessible by ferry. Some, like A.P. Rowe, described it as ‘one of the loveliest places in the world’.12 Others were less keen on its wild, windswept, godforsaken feel. Its location was ideal as it was, as Watson-Watt put it, ‘not too far from London for administrative convenience and yet too far for administrative interference’.13 And, being so remote, all the work carried out there could be done in total secrecy.

  A few weeks later, a small team set off from Slough on a delightful spring morning in two private cars, backed up with two RAF lorries to carry the equipment. This was offloaded onto a small ferry at the village of Orford. The team manhandled it across to the promontory and, using an old fire engine that was a relic of the Great War, installed everything in a set of huts also left over from the war.14 The weather changed dramatically as the small team transported their equipment across to Orford Ness. The heavens opened, and the scientists were met with hail and sleet along with a howling easterly gale. They had the impression they had left the warmth of civilisation to work in an Arctic wasteland, an impression which took some time to wear off. Nevertheless, on 14 May 1935 Britain’s first radar research station opened for business.

  The four scientists working on Orford Ness included Arnold Wilkins, who was forever optimistic about the possibilities ahead, and a twenty-four-year-old Welsh physicist named Edward Bowen, nicknamed Taffy, who had been specially recruited to join the team. He had just finished his Ph.D. research and had spent time at Slough, where he had come ‘under the benign influence of Watson-Watt’.15 Conditions on the station were spartan in the extreme but the men stayed in digs in the small fishing village of Orford. Their cover story was that they were studying the ionosphere, part of the outer atmosphere of the earth which is ionised by solar radiation. On most Friday evenings, Watson-Watt would come up and discuss progress with the team in the Crown and Castle pub. Often these sessions went on late into the night, to the puzzlement of the locals who could not fathom what ‘the Islanders’, as they called them, were up to.

  The purpose of the first experiments was to get a primitive transmission system and a separate receiver up and running. To speed up development, it was decided to operate on a frequency of 6 MHz and a wavelength of 26 m. This involved building large 75-foot towers and the construction of powerful transmitters using borrowed silica transmitter valves from the navy. Getting the system to work involved putting more and more power through the transmitters to increase the energy of the waves. The engineers calculated that they needed to transmit 100 kW of energy in order to produce a powerful enough return signal for the receivers to pick up. They soon realised that the most efficient way to concentrate the waves was to send them out in bursts or pulses. A second set of pulses would only be sent out when the first had been received back. Using components largely purloined from discarded X-ray equipment, they had to build receivers capable of the maximum sensitivity in order to record the echo of the radio waves and generate a line across a screen on a cathode ray tube.

  So keen was everyone to see what was going on that the Tizard committee made the trek out to Orford Ness one weekend barely a month after the researchers had set up shop. Although the equipment failed to detect a passing RAF aircraft, the committee seemed happy with the progress that was being made. On the Monday after the committee had returned to London, Watson-Watt and the team had another go and this time the equipment clearly detected a Scapa flying boat that had taken off from Felixstowe. They were so excited that Watson-Watt rang up the station commander at Felixstowe and asked him to tell the pilot to fly the same route again, and for an hour the team followed its passage up and down the coast with great delight.

&
nbsp; Despite the primitive conditions, progress at Orford Ness was swift. As they managed to generate more power in the transmitters, so the range at which they could detect aircraft increased to 40 miles in September, 80 miles by the end of the year and 100 miles in early 1936. Edward ‘Taffy’ Bowen remembers this period of excitement and challenge as ‘one of the happiest periods of my life’.16 It was a time of great achievement and very obvious progress and none of the young team working there minded the lack of refinements.

  In December 1935 the success of the experiments prompted the Air Staff to commission the building of five stations to provide an air warning network around the Thames estuary. It was still less than a year since the first demonstration in the Northamptonshire field. But the decision to build the first chain of radar stations was recognition both of the advances being made and of the growing urgency of the need for a system of defence. From this a far bigger plan would soon follow.

  2

  Bawdsey Manor

  By early 1936 it was clear that the primitive research station had outgrown its location on the marshes of Orford Ness. A new site was quickly found a few miles south at Bawdsey, where the Air Ministry bought the local manor and about 180 acres of grounds for £23,000. By April everything had been transferred from Orford Ness, and for the next three and a half years Bawdsey Manor was to be at the centre of British radar research and development, becoming a sort of radar laboratory.