It was an iconic moment in the UK's Second World War engineering effort, but how did the development of radar fare in the transfer to the silver screen?
At the end of the Second World War, the Air Ministry was eager to publicise the discovery of a technology that played a crucial role in assisting British forces in defending the nation against German attack: radar.
A young private in the army's cinema unit, Peter Ustinov, was attached to the RAF in order to write the script and direct the film, the first of what turned out to be a substantial collection. The film was 'School for Secrets'
Ustinov used as his inspiration the inaugural gathering of a committee of five scientists in January 1935. Sir Henry Tizard, chairman of the aeronautical research committee, Dr HE Wimperis, director of research at the Air Ministry, his assistant Dr AP Rowe, physicist Professor PMS Blackett and Professor AV Hill, physiologist, met to consider early-warning systems for air defence. In the film, a similar quintet of oddly assorted scientists gather at a remote coastal air station on the eve of war to be taught the basic principles of radar.
Cast of characters
Aficionados of early post-war comic British films will find the cast list familiar: the supercilious Raymond Huntley plays physicist Professor Laxton-Jones; John Laurie plays his colleague Dr McVitie – a Lieutenant Commander here, down from Captain in Laurence Olivier's 1944 'Henry V', and on his way to Private in the BBC's 'Dad's Army' Ernest Jay plays biologist Dr Dainty; David Tomlinson is a doleful Mr Watlington, a young genius from the radio industry; Ralph Richardson is zoologist Professor Heatherville, an authority on reptiles – 'just the poisonous ones', as he informs Sir Nicholas Hathaway from the Air Ministry who has brought the group together.
Outside the five, Michael Hordern appears as a Lieutenant Commander and even Kenneth More turns up in a brief uncredited role. Years later, More emerged again in 'Battle of Britain' (1969) together with Richardson and Olivier. It is difficult striking a balance between a patriotic stiff-upper-lip outing, and a post-war boost to the morale. Sir Robert Renwick, controller of communications at the Air Ministry, asked for 'a little laughter, a little pathos and a lot of hard facts'.
He may have taken a very dim view of the script-writing wit of Ustinov, the renaissance man in the making. If the film represents an honest attempt within an austere post-war environment to produce a history of British radar development, it has more than its fair share of laughter.
Quite how much technical detail is suitable for the comprehension of a movie going public is always a thorny issue – not to mention, in this case, how much technical detail would be made available to Private Ustinov.
Whether all the secrets of radar were fully revealed to the budding filmmaker is doubtful, since the consequent production is a somewhat distorted picture of the history of British radar development just before and during the War.
Ustinov accumulated research during fact-gathering visits to radar stations – not least to the Telecommunications Research Establishment (TRE), Malvern – and items of radar equipment were borrowed from the Air Ministry for use in the film. The coastal air station, where the five characters gather in the film, is likely to have been based on Bawdsey Manor in Suffolk, an early radar research location.
Ustinov was not alone on his tour of TRE. The lowly army private, clothed in drab khaki, had two splendidly attired companions: Chief of Air Staff Sir Charles Portal and Air Vice Marshal Sir Victor Tait, both of whom, no doubt, enjoyed much more in the way of confidential information.
As Ustinov later described in his 1977 autobiography 'Dear Me', being treated as an equal of such notables raised some eyebrows among the accompanying retinue of RAF officers. An encounter with at least one genuinely absent-minded TRE scientist confirmed both his and a widely held public belief that boffins did indeed exist.
Chain Home system
In the movie, the five learn that existing early warning radar systems based on contemporary radio expertise were operating at wavelengths near 12m with transmitting and receiving antennas mounted on independent towers – the 'Chain Home' (CH) system.
Due to target obscuration from surface reflections, the long wavelength was not conducive to detection of aircraft approaching at sea level, so Laxton-Jones asks whether a shorter wavelength would do the trick. Respecting airborne radar systems Heatherville doubts if even a 1m wavelength radar would be compact enough to carry in an aircraft. As for centimetre wavelengths, we are informed that the technology is not yet available.
Heatherville, the authority on poisonous reptiles, sums it all up by supposing that what they really needed for centimetre radar was an 'entirely new type of valve'.
After the outbreak of the war, the scientists are visited by Sir Duncan Wills, pioneer of radio direction finding (RDF) – a thinly disguised Sir Robert Watson Watt. He declares that they need 'a mobile RDF with narrower beam-width', and in the ensuing eight months the group reports on its findings.
Following the Dunkirk evacuation, they are moved well away from the coast and continue their work within the vacant premises of a school. Such an evacuation did indeed take place in real life, after a brief relocation to the scarcely less vulnerable Worth Mattravers on the Dorset coast. In reality, the TRE reconvened at Malvern College, but this is re-imagined as Kippenhampton School.
The main motivation behind the move was anxiety over the possibility of an enemy cross-channel incursion triggered by the Bruneval raid in 1942. This had successfully recovered key components of a German radar.
At 'Kippenhampton', regular meetings are attended by the scientists, air crew and personnel from the radar industry, almost certainly to be attributed to AP Rowe's famous 'Sunday Soviets'. These informal gatherings of senior military personnel with the research engineers and scientists meant that if an idea of merit was put forward – even from the most junior personnel – it could be adopted on the spot, because all the main decision-makers would be there.
McVitie explains to a group of RAF officers a technique for night interception of enemy aircraft by radio-location methods he has been working on. A night-fighter, equipped with a small airborne interception (AI) set, is directed from the ground to engage hostile aircraft, an all-weather system.
McVitie, in the best tradition of experimental physics, takes an active role in proving his system. He flies in a Beaufighter piloted by Jack Arnold (played by a fresh-faced Richard Attenborough), and they down a Junkers 88. New types of transmitting and Local Oscillator valves for shorter wavelengths had been realised, especially the high-power cavity magnetron operating at centimetre wavelengths - Heatherville's requirement achieved.
Nevertheless, even in 1946, the vitally important cavity magnetron is not mentioned by name, nor is the TR cell, which enabled a single antenna to be used both for transmission and reception (typically a parabolic dish). Certain of these items might have been considered excessive for a non-engineering audience.
By perhaps the same token, the myth that an intensive diet of carrots was good for night-time eyesight is included as a security measure to confound the enemy.
AI radar could be adapted for bombers since the scientists had discovered that reflections from the ground provided a means of mapping targets enabling both precision and blind bombing (H2S). A further adaption (ASV) is found to be extremely effective in detecting vessels at sea, notably surfaced U-boats.
A Halifax bomber flight testing an initial version of H2S with Watlington on board flies into a barrage balloon cable and crashes. This incident can be related to the tragic death on 7 June 1942 of Alan Blumlein, 'radio expert from industry par excellence', when a Halifax testing an H2S prototype crashed near the Forest of Dean. Towards the end of the film, the glamorous Mrs Watlington – now a WAAF and fully recovered from her loss – is on the way to becoming the wife of Jack Arnold, now ranked Wing Commander.
There is an interlude in which a CH station at Ventnor undergoes an enemy air raid, an opportunity to introduce broader aspects of the Battle of Britain. The Stanmore Fighter Command control room is used as a focal point, with its air situation plotting table manned by WAAFs. They feed on information provided by CH tracking stations. The resident Air Marshal hopes that 'stuffy' Dowding's faith in radar is justified.
Hyperbolic navigation system
As the film drifts into 1942, the group introduces the concept of a hyperbolic navigation system (GEE) in which three separated ground stations – a master and two slaves – transmit pulses at precisely determined intervals. A constant time difference between reception of the master transmission and one slave transmission is shown as a hyperbolic curve on a CRT screen; likewise for the master and the second slave transmission. Where the two hyperbolae intersect indicates the aircraft position, a telling aid for night bombing over Germany.
Physicist Laxton Jones is depicted on board a Stirling bomber during the first 1000 bomber raid over Germany and using GEE; target Cologne, 30 May 1942. The pilot is again Attenborough as Jack Arnold who seems, we might wryly note, to switch from piloting fighters to heavy bombers with consummate ease. The later sophisticated and more accurate OBOE blind bombing system, employing an aircraft-mounted transponder plus two land-based transmitting stations, usefully guiding a single pathfinder aircraft, is not mentioned. Their aircraft is damaged, so the crew plus Laxton-Jones are obliged to take to their parachutes on the return flight. Laxton-Jones escapes unharmed, fated to land in a reservoir. Arnold breaks a leg.
A U-boat, destroyed from the air by a Wellington bomber, disgorges a German boffin who is interrogated. 'They have been concentrating on infrared and are miles behind on radar,' the British conclude. 'However, we can't bank on that. We need one of the enemy stations intact.'
This statement is a curious one. There were a number of German radars, although they could have done with the highly secret cavity magnetron. Their Knikebein Navigation system was most effective in guiding aircraft on to a target. It transmitted two independent directional radio beams. An aircraft would fly along one beam over the designated target until the flight path intersected with the other.
More sophisticated navigation systems, employing pulsed-transmission techniques, were also being developed. But it is true that false indications of British work on infrared submarine detection were being broadcast in order to make the Germans spend unprofitable time developing equipment to avoid such detection.
In pursuit of the Würzburg
In the movie's Spring 1944, Heatherville and accompanying airborne troops parachute at night into enemy territory on the Normandy coast, the objective being to dismantle and bring back the essentials of the Würzburg, a ground-based air-intercept radar.
There is a firefight, but the mission is successful and, as German reinforcements approach, Heatherville together with his military companions plus the captured components are recovered by a landing craft awaiting them on a neighbouring beach. The raid is a fairly faithful description of the Bruneval Raid which took place in 1942.
To allow the group members to deal with their military colleagues on equal terms, Heatherville is given the rank of Major (Army), Dainty and Laxton-Jones, Squadron Leaders (RAF) and McVitie, Lieutenant Commander (RN).
A number of TRE scientists, mainly ex-Cavendish Laboratory men, get transferred to the USA during the war to contribute towards the Manhattan Project. This gives a little credence to one of the last lines in the film uttered by Heatherville in 1945, after the group disperses – 'I'm going to help blow up Japan'.
One notable name at TRE was biologist Alan Hodgkin, later a joint Nobel Prize winner for medicine. The employment of academics, other than physicists or engineers, on radar work seems unusual but was profitable, as they exerted their own fresh minds to solve problems in a new and, on the whole, unexplored discipline.
Zoologist Sir Solly Zuckerman also did wartime government research, though unconnected with radar. He became chief scientific advisor to the Ministry of Defence in 1960. Well-publicised as an authority on the behaviour of monkeys and apes following this appointment, he was an ideal prototype for Heatherville.
Those knowledgeable in radar technology and its history may be amused on viewing the film, but surely they will be no less entertained than the uninitiated. *