ROTOR ROTOR was a huge and elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bomber s . The system was built up primarily of war - era radar systems , and was used only briefly before being eventually replaced by the more modern Linesman / Mediator system . Post - war situation . UK radar operations were wound down late in the war , and by the time the war ended were already largely unused . It was assumed that another war was at least ten years away , and the need for any improvements in the cobbled - together system seemed remote . Thinking changed dramatically in 1949 with the Soviet test of their first atom bomb . It was known that the Soviets had made exact copies of the B - 29 Superfortress as the Tu - 4 Bull , and these aircraft had the performance needed to reach the UK with a nuclear payload . Studying the problem , the 1949 Cherry Report suggested that the 170 existing Royal Air Force radar stations be reduced to 66 sites and the electronics extensively upgraded . East Coast sites were constructed in various ' hardened ' designs in the ' R ' series ( R1 , R2 , R3 and R4 etc . ) , the original designs were not ' nuclear hardened ' bunkers but very substantial structures protected against conventional attacks . West Coast sites were in semi - sunken hardened structures ( ' R6 ' ) or above ground ' Secco ' type huts ( Hartland Point etc . ) . Most of the new network would be made up of 28 re - built Chain Home systems , while the rest were taken from the existing selection of Chain Home Low , Chain Home Extra Low and the various Ground - controlled interception ( GCI ) radars that had formerly served special purposes . This was , in part , a stop - gap measure anticipating the availability of the dramatically improved Type 80 Green Garlic radar which would replace the various early warning radars with a single system of much greater performance . Interception guidance would still be handled by existing systems in either case . All of the radars were to be improved in terms of siting with the addition of hardened control bunkers to protect the operators from a conventional attack . On the east coast , the coast toward which a Soviet attack would be most likely , the bunkers were underground , while those on the western side of the UK were generally above ground as a cost - saving measure . The bunkers themselves were otherwise similar , featuring concrete walls with all equipment , operations generators and air conditioning located inside . Additionally , ROTOR re - arranged the existing RAF Fighter Command structure into six " Sector Operational Commands " ( SOC ) with their own command bunkers ( three level ' R4 ' protected accommodation ) . Only four of these were built . Additional " Anti - Aircraft Operations Rooms " were built to coordinate the British Army ' s AA defences in the same overall system . The entire network of bunkers , radars , fighter control and command centres used up 350 , 000 tons of concrete , 20 , 000 tons of steel and thousands of miles of telephone and telex connections . The work was mainly carried out by the Marconi Wireless and Telegraph Company in several phases , called ROTOR 1 , ROTOR 2 and ROTOR 3 . Post - ROTOR . As the anticipated Type 80 " Green Garlic " radar started testing shortly after ROTOR came online , it became clear that it could fill both early warning and interception guidance from a single site . This dramatically decreased the complexity of the ROTOR system , which otherwise required sightings from the early warning radars to be telephoned to the fighter control GCI stations for local plotting . By concentrating all of this complexity at a single site the total number of operators was greatly reduced . As a result of the introduction of the Type 80 ( Green Garlic ) , many of the existing ROTOR sites were rationalized into " Master Radar Stations " ( MRS ) , while the rest were made redundant , some only two years after opening , and all of the AAOR sites were closed . A few of these were re - used for government department ( ' RSG ' s ) and local authority wartime headquarters . In the mid - 1960s the MRS ' s themselves were replaced with a new system called Linesman / Mediator . Until the end of the Cold War many of the sites were retained by the government but now have been sold off to private buyers or converted into museums ( for example ' RAF Hack Green ' ) and some transferred to the National Air Traffic Control Centre . Sector Operation Control centres . Custom Built : World War II : Sector Operations Centres . From Sub Brit website ROTOR Radar Sites . This links to modern aerial site photographs of both ' retained ' Chain Home & ROTOR sites . Note there now may be nothing visible of the original site on the ground and only crop marks visible from the air . RAF Staxton Wold is the only Chain Home site still used as a military radar site but with no remains of the CH station on site after being rebuilt for Linesman / Mediator in 1964 . Note : A number of ROTOR sites had very short operational lives , sometimes less than 1 year and thus don ' t appear on many maps . Example : West Myne in Somerset was the last ROTOR 3 CHEL site . It was completed / tested in 1957 after the introduction of the T80 radar and after many ROTOR stations had already closed . The site was within Exmoor National Park and its creation was strenuously opposed by the National Trust who lost no time in obliterating the site immediately after closure . List of ROTOR SITES .