This extract taken from Porton Field Trials Report No. 610 shows the track taken across Norfolk by Porton Down’s spray-plane during the first of the Norfolk/Norwich field trials. This trial took place on 28 March 1963. The Devon aircraft flew a 62 miles straight-line track across Norfolk, 24 miles upwind of the target city – Norwich. As the aircraft flew along the track it continuously disseminated large amounts of a Biological Warfare (BW) ‘simulant’. A BW simulant is a supposedly harmless substance which mimics the physical properties of a real BW agent, in this case, size (between 1-5 microns). BW simulants are used in BW experiments in which, for safety reasons, a real BW agent could not be used. Unfortunately for those exposed to the simulants, the particle size meant that it would evade the body’s natural defences and penetrate into the deepest part of the lungs – the alveoli.

The BW simulant used in all of the Norfolk/Norwich field trials was Zinc Cadmium sulphide. According to an internal MOD historical review CDEE Porton Down were aware as early as 1955 that this simulant should be treated as hazardous material. All Porton staff concerned with the handling/dissemination of this simulant were instructed to wear protective clothing such as: respirators, overalls, rubber boots, surgeons caps, elbow length neoprene gloves, etc.

The procedure was for the aircraft to fly a crosswind straight-line track all the time spraying large quantities of Zinc Cadmium sulphide particles. The resulting aerosol cloud was carried downwind to the target area. Teams of CDEE Porton Down scientists, Home Office scientists and members of the City of Norwich Police operated air-sampling equipment, located at numerous locations across Norwich and the surrounding countryside. This equipment was designed to attempt to collect samples of the ZnCds particulate cloud The air sampling locations included Police stations and private property.

After each trial, the sampling equipment was taken for assessment and the number of particles per unit of air was measured.

CDEE Porton Down went to great lengths to ensure that members of the public were not made aware of their participation in these trials. A declassified Porton Down doc instructed:

“All C.D.E.E. personnel will wear overalls, duffel coats and gum boots, free from traces of F.P. and not bearing any lettering, such as “C.D.E.E.”, where it is visible whilst the garments are being worn.”

Residents of Norfolk were only made aware of the existence of these trials in 2001.