In May 1942 the Telecommunications Research Establishment - Britain's radar brain trust - left its clifftop laboratories at Worth Matravers on the Dorset coast and moved to Malvern, ten miles north of Defford. The trigger was paranoia, and not unfounded paranoia: the British raid on Bruneval that February had snatched components of a German radar set off a French clifftop, and the assumption was that the Germans would retaliate in kind against Worth Matravers. The TRE took up residence in Malvern College's requisitioned classrooms. Its flying arm - the Telecommunications Flying Unit - landed at Defford. The move was hurried enough that personnel slept in tents at first, but the work accelerated almost immediately. By 1945 the airfield held 100 aircraft and 2,500 people, civilian scientists flying alongside RAF and Royal Navy aircrew on aircraft modified beyond recognition.

What they were perfecting was airborne radar, and what airborne radar did was solve three of the war's worst problems at once. Airborne Interception sets let RAF night fighters find German bombers in the darkness over England; John "Cat's Eyes" Cunningham, whose preternatural night-vision was a wartime cover story, was actually flying with AI radar developed at Defford. Air to Surface Vessel radar let Coastal Command find U-boats running on the surface at night, the moment when the submarines were most vulnerable and most needed to recharge their batteries. By mid-1943 it had turned the Battle of the Atlantic. H2S - the downward-looking ground-mapping radar perfected here in 1944 - let Bomber Command find their targets through cloud. None of it would have worked without the cavity magnetron, a small valve that produced microwaves powerful enough to be useful and compact enough to fit in an aircraft. A converted Wellington bomber tested at Defford was the world's first airborne early warning aircraft - a direct ancestor of the modern AWACS.

On 7 June 1942, four weeks after the unit's arrival at Defford, Handley Page Halifax V9977 took off carrying eleven people - RAF aircrew, civilian scientists, and the H2S radar prototype they were testing. The aircraft caught fire in the air and crashed near Tewkesbury. Everyone on board died. One of them was Alan Blumlein, the EMI engineer who had patented stereo sound recording in 1931 and was at that moment one of the most brilliant inventors in Britain. His death was not made public for decades - the work he was doing was that secret. Sixty years to the day later, in 2002, Sir Bernard Lovell - himself a TRE radar scientist who survived to build the Jodrell Bank radio telescope - unveiled a memorial on the village green at Defford. It honours "those Royal Air Force Air Crew, Scientists, Engineers and Civilian Personnel who lost their lives in the furtherance of Radar Research while flying with The Telecommunications Flying Unit (later the Radar Research Flying Unit) from RAF Defford 1941-1957."

Among the many "firsts" Defford could claim, one stands out as a small triumph of nerve and craft. In January 1945, in the snowy last winter of the war, a converted Boeing 247 with the registration DZ203 made the world's first fully automatic landing - no pilot input, the aircraft flying its approach and touchdown entirely on instruments. Civilian air travel still routinely deploys some descendant of that capability whenever fog closes the destination. After the war the flying unit continued, renamed the Radar Research Flying Unit in 1953. By 1957 the airstrip was simply too short for the new V-bombers - Valiant, Vulcan, Victor - that needed test flights, and the RRFU moved its aircraft to the longer runway at RAF Pershore. Defford's aviation chapter closed.

But the flat ground and the line-of-sight horizon were ideal for another job. In 1980 the Royal Signals and Radar Establishment moved its satellite-tracking facility here, taking advantage of the flood-plain flatness and the nearby bulk of Bredon Hill, which made an excellent satellite simulator. The dishes that grew on the old airfield were involved in the Skynet 4 military communications satellites and their ground stations. The site is now operated by QinetiQ; the dishes are still working. You can see them from the M5 motorway near Strensham services, or from any train running between Worcester and Cheltenham. The old domestic and technical buildings are mostly gone. A few survive as part of the National Trust's Croome estate next door, including the medical block, which now houses a small museum of RAF Defford's history. Walk through it on a quiet afternoon and the photographs of young scientists in flight jackets seem almost present - the radar pioneers who flew from this field, and the ones who did not come home.