Work in Worth Matravers continued apace during the long hot summer of 1940. These were dark days for Britain….the evacuation of Dunkirk in May was followed by the Battle of Britain in the skies over southern England through June and on until September. These terrible events seemed to spur on the scientists at Worth to excel themselves. New aerials were developed, shorter, more effective wavelengths were employed (using the newly developed Magnetron) and special navigational and bomb-aiming aids were rapidly conceived.

German radar was also developing rapidly and a commando raid on the French coast in February 1942 brought back tangible evidence of their capabilities. Concerns were raised that a reprisal attack on Worth was very likely and Winston Churchill ordered the unit to be moved to safety yet again……..

The complete story of the development of radar can be found on http://histru.bournemouth.ac.uk

The Battle of Britain and GCI

By June 1940, the Axis powers controlled most of Europe. Poland, Austria, Holland Belgium, and Norway had all been overrun. When the British Expeditionary Force was evacuated from Dunkirk (Operation Dynamo: 27th May - 3rd June) the way was clear for the annexation of France. Ten days later Paris was occupied. The way seemed clear for the Germans to turn their attentions to the invasion of Britain.

Hitler realized that before a successful sea borne invasion could be launched, it was essential that the Luftwaffe gained total control of the skies (Operation Eagle) and that the RAF had to be neutralized. He ordered the total destruction of the RAF and placed Reichsmarschall Goering in charge of the operation. Raids began in earnest on 18th June. The loss of France had meant that the Luftwaffe could begin replenishment of men and machines and use their newly acquired French bases to plan the destruction of the RAF. During that summer CHL (and CH) were the only systems that were available to 'home' the fighters onto their targets. Ground Control Interception stations evolved from the CHL stations. It was primarily C.J.Banwell, a New Zealander who developed a new transmitter switch that allowed sufficient suppression of the transmitter pulse that a single aerial could now be employed for both transmission and receiving. This new single aerial could subsequently be continuously rotated. Finally, if the trace could be made to commence from the centre of the screen instead of at the left hand edge, a continuous rotating 360-degree scan could (in theory) be produced. This work continued through the summer and into the autumn. By December, three GCI installations were completed (albeit hastily) at Durrington, Sopley and Sturminster Marshall. A further 12 mobile units were ordered by the RAF for immediate use. Thus by the spring of 1941 GCI was an operational reality.

G.E.Bacon, K.Hopkinson and R.L.Elliot contributed to some complex improvements to the aircraft height determination systems, later to be known as the Type 13 height-finder. Permanent plotting rooms, where the chief controller could 'look down' on the battle (often referred to as 'Happidromes' because of their resemblance to a theatre) were quickly constructed and became the natural successor to the old 'filter rooms'.

Click HERE to hear G.E.Bacon's Account

The Skiatron

Once Plan Position Indicators [PPI's] were available, efforts were made to project the images directly onto a larger working surface to facilitate the work of the WAAF plotters during action.
The Skiatron was a modified oscilloscope giving a particularly bright radar display.

The images could be projected upwards and the tube was mounted underneath a transparent [glass] plotting table. This equipment was quickly installed in the GCI stations.

Small blocks or counters were then moved [at regular intervals] to both identify the relative positions of both 'friend' and 'foe' but also to track the movements of squadrons and individual aeroplanes as the attack unfolded.

The Navy also adopted this tool and one was installed in the control room of HMS Ark Royal when she was in dry dock in Liverpool.

The role of the plotters was a critical one, the work was demanding and instructions to the pilots and information from the radar traces had to be rapidly and accurately interpreted by the ground controllers who generally were positioned around and above the plotting table; 'theatre-style'.

The Skiatron Part 2

'Pipsqueak' communication methods were fully employed. Special terminology was coined such as 'scramble' 'bandits' and '6 o'clock high' to enable the pilot and his ground controller to communicate quickly with the minimum of ambiguity or 'chatter'.

When the night-time raids commenced, it was necessary to modify the ground control arrangements using 1.5m systems (Ames Type 15 for example) because they were more accurate. The daytime arrangements involved the use of 'filter rooms' where information was collated from a number of sources including ground observers. At night however, the GCI units information was fed directly to Fighter Command and one ground controller would then speak by radio-telephone to a specific 'Wing Leader' and direct him onto the optimum course and altitude to engage the enemy.

Some GCI units were fixed such as the unit at Sopley (near Ringwood) but other rigs were mobile and could be deployed as battle tactics dictated.

Achievements at Worth

The period from May 1940 to March 1942 was arguably the most fertile period in the quest to produce airborne radar that could be employed for offensive purposes. TRE Worth (and the associated Leeson House) were after all, primarily Research establishments although operational CH and CHL work was also carried out there.

It was also the period when Britain was under severe duress; the evacuation of Dunkirk, the Battle of Britain, the Blitz and the Battle of the Atlantic tested the nation's resolve to the limit.
The experimental CHL unit at 'D' site was soon spawning new devices; C.J.Banwell developed a special transmitter switch that soon allowed a single aerial to be used instead of two. Then a rotating device (at first manual and then electrically driven) was conceived. These two developments allowed Dummer and Franklin to perfect a rotating time-base display layout on a cathode ray tube. Hence GCI coupled with the new Plan Position Indicator was the first major achievement at Worth. Although too late to help during the Battle of Britain in the summer of 1940, GCI and PPI were essential operational tools for all the Armed Forces from late 1940 for the remainder of the war.

New aerial designs for both ground, airborne and shipborne uses were developed at this time. Perhaps the greatest step forward came in July 1940 when the first prototype Magnetron arrived. With this invention it was possible for Bowen's centimetric team to forge ahead with more effective and accurate Airborne Interception (AI) equipment. In August 1940, the team produced the first 10 cm echo from a building: the old chapel at St Aldhelm's Head.

The first ASV submarine detection trial was successfully conducted in November 1940 in the Solent.

The GEE system of radio navigation was under development during 1941 and came into operational use in March 1942. It was also at TRE Worth that the development of OBOE, and H2S systems began. They came into operational use in December 1942 and January 1943 respectively.

It was also at TRE Worth that Robert Cockburn set up his highly respected 'Radio Countermeasures Group

Click HERE to hear W. E. Burcham's Account
Click HERE to hear A. E. Bennett's Account
Click HERE to hear H. G. Hinkly's Account

Leeson House

It was essential that research and development continued apace during the summer of 1940. The site at Worth Matravers was growing rapidly but not sufficiently quickly to accommodate the ever-increasing numbers of scientists and technicians that were being drafted in during that summer. Two large country houses, Leeson House (an empty girls' school) just 3 miles away from TRE Worth and Durnford House (a preparatory school in Worth Matravers) were hastily requisitioned in September 1940. Both sites were used as laboratories and were rapidly filled with equipment and personnel and hoards of mice!

A.P Rowe was the Chief Superintendent of TRE and he believed in the importance of the 'centimetric radar' but was dubious that such a system could be developed quickly enough to have any impact on the war effort. Nevertheless, he gathered a prominent team together that included some leading scientists of the day; P.I.Dee, H.W.B.Skinner, W.B.Lewis, Bernard Lovell, D.W.Fry, John Cockroft and J.A.Ratcliffe are just some of the people involved. The work was to continue and some aspects were remain somewhat 'unnoticed' by officialdom. Leeson house was very suitable in that respect; near to TRE Worth but separated.

Each laboratory was soon filled with test gear and experimental circuits concerning AI and the transmitters and aerial designs that would permit installation into the cramped space of an aeroplane.

Whilst the principles of airborne radar were now understood, the issues of weight, size and power supply all still had to be resolved.There was a spectacular view from Leeson House across Swanage bay and to the Isle of Wight, some 40 miles away. This geography was utilised to test the 9 cm and then the 3 cm radars. The 9 cm systems adopted by the Navy were developed here at this stage.

The staff at Leeson House, only there for 18 months, were moved to Malvern in March 1942 along with all the other TRE personnel.

Daily life at TRE Worth

Although 'Taffy' Bowen seemed unimpressed with the situation at Worth in May 1940, most of the others scientists who arrived soon settled in and seemed satisfied with their 'lot'. At least the site was purpose built for cutting edge radar research. The huts seemed spacious in comparison to the cramped premises at Dundee. The blast walls made the huts gloomy and there was always thick glutinous mud everywhere in winter. The main mode of transport between the 5 sites (and into Swanage) was the bicycle.

Initially, work proceeded on a seven-day basis and the rest day was 'staggered' so that six sevenths of the staff were on duty at any given time. By 1941, Saturday became the rest day in order that staff were on duty on Sunday to participate in the 'Sunday Soviets'.
There were special church services held in Langton Church for the men after work on a Friday, once a month.

The influence of TRE grew steadily through the summer of 1940. Attentions were shifting away from purely defensive systems such as CH etc and more towards offensive needs. Hence, by 1942, some 25% of the work carried out here was for Bomber command.

The arrival of the cavity Magnetron in July 1940 meant that work could forge ahead to produce operational 10 cm radar that could be used on land, on sea and in the air.
enemy.

The scientists were happy and productive at Worth and the results are apparent….the move to Malvern was not welcomed in the same way….either by the scientists or by the Malvern residents.

Click HERE to hear A. I. Llewelyn 's Account (1)
Click HERE to hear A. I. Llewelyn 's Account (2)
Click HERE to hear A. E. Bennett 's Account
Click HERE to hear G. E. Bacon 's Account
Click HERE to hear S. Ratcliffe 's Account (1)
Click HERE to hear S. Ratcliffe 's Account (2)
Click HERE to hear S. Ratcliffe 's Account (3)

Social life at Worth

The building work at TRE Worth was very hectic during the summer of 1940 and the base and its staff complement grew rapidly. A few complained about the mess but most enjoyed the enthusiasm and 'energy' of the new establishment. The site was considered by many to be very attractive. They would often walk down to the Square and Compass pub for a ploughman's lunch and a pint of mild and bitter.

Many of the scientific problems that were being encountered were solved "at the pub". This hostelry had been a favourite haunt of actors and film stars before the war.

The harrowing scenes of soldiers returning from Dunkirk were still fresh in the minds of the young science graduates who were arriving at Worth daily. They were given every incentive and facility to use their special talents to advance the CHL and AI programmes as quickly as possible.

Many of the young men were interested in cars; John Pinkerton had a 1925 vintage Lancia, Don Priest had an Alvis speed 20 and Doug Hogg had a 3-litre Bentley.

The villagers provided much accommodation although some were billeted in Swanage about three miles away. Many would cycle into work each day along the cliff path. George Bacon and the New Zealander, C.J.Banwell spent their first night (4/5/40) in the Vicarage. The men and their work were initially treated with suspicion, but soon the Dorset 'locals' treated them with the utmost hospitality and they seem to have found the surrounding countryside conducive to their vital research. Gradually, a great camaraderie grew up amongst these men and they soon joined in the social life of the village...

Most of Renscombe Farm had been requisitioned by the War Office and the farmer had to move his stock to Hampshire. However, he agreed to provide milk and his wife even set up a little tea cabin for the men between 'a' and 'b' sites.

Kenneth Hopkinson recalls that in June 1940, Swanage had a lot of spare accommodation and so his family could join him and enjoy the beach for a little while…until a defensive barrier was placed across the bay. He also remembers that the bus fares seemed very high. His abiding memory of TRE Worth is"mud and bikes".

Click HERE to hear A. I. Llewelyn 's Account
Click HERE to hear H. G. Hinkly 's Account
Click HERE to hear G. E. Bacon 's Account

TRE Worth, then and now

Sound Detection... a forerunner of Radar

When the TRE unit was moved to Malvern the RAF adopted the site and they remained there for a further 25 years. The site was then cleared and the land was returned to agricultural use.

Of the 5 original sites (A, B, C, D & E), there is little to see today except some ruinous building clinging to the cliff at what was site 'D'. This was one of the experimental CHL stations and was constructed on the site of an old quarry. The elevation above sea level was perfect for detecting aircraft approaching low over the sea.

The largest site within the establishment was 'C' site and this is where the important research on 10 cm radar took place. Today, there is nothing to see except green fields.

The seaward end of this field was occasionally used to land light aircraft used to calibrate the radar sets that were being tested here.

TRE Worth, then and now Part 2

There may be little remaining of the TRE site at Worth Matravers but the importance of the work done here in helping to turn the tide of battle in favour of the allies has not altogether been forgotten. There is a memorial in the shape of a radar dish overlooking the sea at St Alban's Head and very near to 'D' site…

Then as now, the local 'pub' plays an important role in the life of the village….

The 'Square and Compass' was affectionately known as the 'Sine and Cosine' by the men at TRE. This was an obvious allusion to the fact that radar physics is deeply connected to geometry.

The Plan Position Indicator (PPI)

Men, machines and raw materials are always precious and this was certainly the case in 1940. A way had to be found to resist the onslaught of numerically superior Luftwaffe.

Maneuvering an aircraft into a tactical fighting position
One of the ongoing problems with airborne (AI) radar is that the detection range was never much more than 3 miles and if the aircraft were below 10,000 feet, this figure reduces to 2 miles due to ground signal reflections. If ground controlled interception (GCI) was to work effectively, it would be essential that the ground team could accurately direct the fighter onto the target and into a strategically advantageous position, ideally 1 or 2 miles behind the enemy plane.

The night bombing raids presented a particularly difficult problem because visibility on a moonless night might be as little as 300 yards. It was essential that the most advantageous firing position was calculated rather than left to a "who sees who first" method. Therefore the ground control team needed to have a system whereby they could 'look' at the whole battle and move their forces accordingly.

With the introduction of rotating antennae on the transmitters and receivers used for CHL and Naval radars it was now possible to build an oscilloscope that displayed a trace which swept a radius from the centre of the screen and rotated about the centre in time with the rotating aerial. The phosphors used to coat the screen were especially chosen to produce a long 'afterglow', so that each trace remained visible to be refreshed with each cycle of revolution.

All that was needed now was to draw on (or overlay) this special screen with the map of the area scaled to coincide with the known radar range. The radial time base display developed by G.W.A.Dummer was tested and eventually the PPI was born and within a year was made compact enough to be installed in aircraft as well as used for the original ground-based applications.By mid-1940 CHL was rapidly evolving from a defensive instrument into a potent offensive tool that gradually gave the RAF pilots a tactical advantage over the attacking aircraft.

The Plan Position Indicator (PPI) Part 2

So two screens were now employed: the PPI giving ranges and bearings and the other giving heights of all aircraft in the vicinity….

This information would be sent to the 'filter room' where it would be assimilated along with incoming information from CH stations and observers on the ground. It would then be the task of the duty officers to consider and orchestrate their response. Usually the battle picture was played out on a large plotting table. It was later that the Skiatron was used.

Click HERE to hear Air Vice Marshall P. M. S. Hedgeland 's Account

The August 12th raid

60 Group RAF were based at Leighton Buzzard and were made responsible for all ground-based Radar coordination. Whilst many of the installations had been protected with blast defences it was only a matter of time before the Germans attacked these installations. On that morning Rye, Pevensey and Dunkirk (Kent) were all attacked. In the afternoon it was the turn of Ventnor on the Isle of Wight. This was the only station that was put out of action for any serious length of time.

More raids were expected to follow but they did not come. Field Marshall Goering had not been convinced that radar was of any great significance and would not sanction any more raids against these stations.

It is quite probable that if those attacks had been pressed home and the defensive Radar shield removed from southern England that the Battle of Britain would have been lost within one month.

Click HERE to hear G. E. Bacon 's Account
Click HERE to hear S. Ratcliffe 's Account

The German capability

Whilst the British research had, by 1940 produced a protective radar shield around the coastline, it was equally important to know what defensive and attacking radar devices the Axis powers had at their disposal. German technology was as advanced as the British technogy but had adopted a different emphasis. It seems that the main use of detection radar was to reduce the need for a large observer corps. In Britain the emphasis was on giving the RAF (and subsequently the Army and Navy) a new weapon with which to gain a strategic advantage over the enemy. Certainly, the Luftwaffe failed to grasp the true military significance of Radar until 1942.

Bombing raids on Wilhelmshafen in September 1940 confirmed further details; that the Germans RDF systems could detect aircraft at ranges up to 150 kM using transmitters of 20 kW output. They also had a 'friendly' homing beacon device that was also a beam-aided bombing system codenamed "Knickebein" (= "bent leg"). This was the system used during the London blitz but because the technical details were deduced, it was possible for Robert Cockburn to develop a powerful 'jamming' system known as 'Aspirin'.

"Wurzburg" was the accurate German coastal protection / early warning system that had a range of about 35 km transmitting on a wavelength of 53 cm. "Freya" was a physically larger, more powerful system (but less precise) with a range of 90 - 150 km transmitting on a longer wavelength of 2.5 m.

Knickerbein was later refined into the "X- beam and Y-beam" systems known as " precision bombing systems known as known as "Wotan 1 & 2".

The Bruneval raid

There had been a number of raids against the industrial complexes of the Ruhr valley during the winter of 1941 / 1942 and many allied bombers had been destroyed by German anti-aircraft fire, even at night and under overcast conditions. The Germans had developed and improved their radar system. One that could be used for directing anti-aircraft fire was known as 'Wurzburg'. Aerial reconnaissance had suggested that one of these units had been installed near Bruneval in Normandy….

Click HERE to hear S. Ratcliffe 's Account

RAF Christchurch

RAF CHRISTCHURCH had begun life as the home of the local flying club and was adopted by the RAF in 1935. The primary duties of the unit were to work on special projects. Airspeed Ltd was also based here, they were involved in designing camouflage systems for aircraft, and they also constructed the 'Horsa' military transport gliders later to be used during the invasion of France.
In 1940, many unusual aircraft with specialised modifications could be seen here, along with the young scientists charged with the task of making everything work...

Such a facility was considered essential for the testing of the pre-production AI radars being developed at TRE Worth some 26 miles away. There were three hurricanes allocated to the unit for protection. The main drawback with Christchurch was that it only had very short, grass runways (5), quite unsuitable for full military use.

The AI flight-testing involved Blenheims, Beaufighters and Mosquitoes. Lancasters and Wellingtons would have been unable to land here. The limitations were partly resolved when a new aerodrome was opened at nearby Hurn in August 1941.

Initially, work involved the development and testing of AI's Mk V, VI and then came the centimetric AI Mk VII. This system was flight tested over the Solent in late 1941 and was destined soon to become known as H2S. The first trials-equipped Halifax arrived at Hurn in March 1942; just as TRE left Worth Matravers for Malvern!

In March 1944, the 405th fighter group of the USAF arrived at Christchurch with their squadrons of P47 Thunderbolt fighter-bombers in preparation for D-Day.

The Dorset Coast Digital Archive is grateful to the Oral History Research Unit at Bournemouth University for permission to use material from their website.