For most residents of York, it was an ordinary Saturday morning. Only the sudden arrival of unseasonable weather – snow flurries in late March – might have raised an eyebrow. Few could have known that, 17 miles away, a five-megaton nuclear weapon had just destroyed Leeds.

Close to York’s historic Guildhall, three women ducked out of the snow and entered an anonymous outbuilding, hoping to escape the imminent arrival of a rather more lethal substance. Inside, they found a fully prepared fallout room, which would offer basic protection against the radioactive dust that was billowing towards York. For the duration of the crucial first 48 hours until the radioactive danger subsided, the women would seal themselves in the room. Fortunately, they’d brought their knitting and some books, so at least they would have something to do.

Of course, Leeds hadn’t really been wiped off the map and there wasn’t any fallout. The events were a simulation and the three women were willing volunteers from the local Civil Defence Corps. They were taking part in an official experiment, run by York’s Civil Defence Committee, to find out how ordinary people would cope in the days following a nuclear attack. Specifically, the experiment was to put the advice of a high-profile government booklet to the test. By the end of their two days in nuclear isolation, the women would emerge confused, cold, apathetic, listless and afraid.

In 1965, the UK government was primed for nuclear war. Rattled by Cold War tensions, Britain's civil defence measures were running at full tilt. Evacuation plans were in place, strategic food stockpiles teemed with corned beef, flour, sugar and fat, and the government was engaged in a nationwide spate of bunker-building. York had not been excluded from this whirlwind of 'preparedness' (a specific term used by the emergency planners).

In October 1961 a small, three-person bunker had been built in the nearby village of Fulford for the use of the Royal Observer Corps (ROC), the volunteer organisation charged with watching the skies and – if it came to it – triangulating, measuring and reporting nuclear explosions. It was just one node in a huge network of underground monitoring posts constructed across the UK, which, at its mid-1960s peak, numbered more than 1,500 bunkers. Later in the same year, a bunker three levels deep was built at Acomb, in the York suburbs, to act as the local ROC headquarters.

For the public, official guidance had been issued in 1963 by the Home Office, detailing what to do in the event of a nuclear strike. This took the form of a public information booklet, Advising the Householder on Protection against Nuclear Attack, officially known as Civil Defence Handbook No. 10. While a couple of guides had been made available in the years since the war, this new handbook had been published to answer the need for something, as an internal Home Office memo put it, ‘shorter, cheaper, and in pamphlet form’.

A brief introduction set out the reasons for its existence: ‘Until general disarmament has been achieved,’ it said, ‘there remains some risk of nuclear attack … This booklet tells you what you could do to protect yourself, your family and your home.’ The booklet explained the basic effects of a hydrogen bomb: the heat, blast and fallout. It provided suggestions for which supplies to stock up on, and described the system of warnings – sirens, church bells, gongs and whistles – that would indicate danger of attack and of fallout.

It also described how to construct your own fallout room to help your family survive those first, dreadful days – long enough to step out into a landscape changed forever and, in theory, begin rebuilding Britain. In a normal house, a ground-floor room with as few external walls as possible was considered ideal. In a tower block, flats in the middle would offer the most protection. Bungalow-dwellers and those living in postwar prefabs were out of luck; the protective factor of this housing stock was calculated to be so low that the booklet advised staying with a neighbour instead. Having chosen your fallout room, any windows were to be blocked up from the outside with sandbags, or from the inside by furniture, or – better yet – bricked up altogether.

To achieve maximum protection, however, a ‘shelter core’ would need to be constructed. There were several suggested forms the ‘core’ could take: a lean-to made of a couple of doors and covered in sandbags; a trench dug beneath the floorboards; a cupboard under the stairs. The idea was to spend the first few hours, when danger from fallout was at its highest, in the ‘core’, before emerging into the main fallout room once the radiation had decayed. ‘Prepare your fallout room for a stay of at least a week’, suggested the booklet, ‘but remember to leave enough space to move about in.’

Soon after the publication of the booklet, York Civil Defence Committee decided to create a permanent exhibit, as a practical interpretation of the advice given in the booklet that members of the public could examine for themselves. A major part of this exhibit was a full-scale fallout room, available to view until it was shuttered during the purdah before the general election in October 1964. It remained mothballed through the winter, until, in spring 1965, the committee had an idea that would take their simulation a step further: by getting some volunteers to stay in the room for a prolonged period – say, a weekend – they could test how sound the government’s advice really was. And if it drummed up a little more publicity for the exhibition, which was about to go back on public display, then all the better.

Volunteers for what became known as ‘The York Experiment’ were sought from the local branch of the Civil Defence Corps; the first three to sign up were selected to enter the fallout room. The trio all happened to be women: Margaret Jones, a housewife; Winifred Smith, a welfare officer who worked on the railways, and Mildred Veale, a civil servant. They were described in the official report as ‘youngish’ – Jones was 34, Smith and Veale were both 40 – ‘active, healthy and sensible’. It was thought they would ‘accept the adverse conditions prescribed and co-operate in such a way as to yield meaningful results’. A weekend in late March was chosen as the ideal time for the experiment, just before the clocks went forward. However, after a relatively warm and dry week, Saturday morning had seen temperatures plummet – meaning a rather cold start to British Summer Time and to the three women’s experience.

At 10am, the volunteers said goodbye to the outside world and entered the room that would be their home for the next two days. Measuring nine by 13 feet, the space was about the same size as a normal living room. It had been kitted out with a table, chairs, cupboards and bookshelves; one of the volunteers had brought a complete set of James Bond thrillers to read. No light came through the windows, which had been whitewashed to the specifications of the government handbook. Ventilation, on the other hand, was not an issue: one window had been jammed open half an inch to allow the power cable for the room’s radio set to pass through.

Standing at one end of the room was a lean-to shelter core, which had been made by propping a couple of doors up against the wall, reinforced by a stack of sandbags. The core measured just three by five feet, but offered a protective factor from radiation three times that of the rest of the fallout room. The women immediately climbed into the shelter core, where they would need to stay for seven hours in order to avoid the most damaging effects of the ‘fallout’. The Times reported that they managed six-and-a-half uncomfortable hours in the core before emerging, suffering from cramps.

Then apathy set in. Though described as ‘women of intelligence and determination’ and despite having brought pastimes with them, the women didn’t do anything during that first day. ‘They did nothing but exist; the minimum of cooking, but nothing else whatever’, the organisers admitted. The rapid onset of listlessness in the three volunteers after their stint in the ‘core’ took everyone by surprise. ‘Cold, miserable, aching and stiff’, the women chatted a little, ate, took painkillers and slept.

Simulated radio news broadcasts, pre-recorded to tape, and preceded by five minutes of music, were played via the fallout room’s wireless set seven times during the experiment. The women were instructed to push a buzzer to indicate they had heard them – their only form of communication with the outside world. If the broadcasts were meant to make them feel better, it did not work: once the news had finished, the volunteers became ‘more miserable and isolated’. The fifth broadcast, in particular, ‘had quite a profound effect’ according to the official report: a technical glitch meant the lunchtime transmission finished more abruptly than intended, leaving the women ‘fearful’ for the next three hours. They tried to do some knitting, but made so many mistakes they had to give up. They took tranquilisers, which had little effect. They went to bed, but found themselves unable to sleep. After just under two days, the experiment had started to take on a sense of realism that nobody had expected.

Meanwhile, outside the fallout room, unknown to the volunteers, members of the press were gathering. A local newspaper had caught wind of the experiment, which had been mentioned in council minutes. On finding out, the organisers thought it best to let the government’s publicity wing, the Central Office of Information, know what they were doing. Word of the experiment quickly spread around Fleet Street. Some reporters arrived on Saturday and Sunday and were even allowed some degree of participation, such as hearing the taped ‘radio broadcasts’. Many more arrived on Monday morning. By the time the women emerged into the sunlight, some 40 reporters were waiting to greet them.

While it might be assumed that the women would not have been prepared for the media circus, the official report disagreed. ‘When the ladies opened the door, we were relieved to see that they were extremely presentable and ready for the fray’, it asserted. ‘The ladies knew what they were doing, believed it to be important, and obviously impressed the reporters with their sincerity.’ The Civil Defence Committee was only too happy for the extra publicity and ‘no restriction whatever was placed on questions and answers’.

They were rewarded with plenty of coverage. As well as every national daily newspaper, crews from the BBC and Granada Television were keen to interview the nuclear attack survivors. And, having already made the cover of the Sunday People, the story ran nationally the following week in the Sun, Times, Telegraph, Express, Sketch, Mirror, Mail and Guardian, under headlines like ‘Terror in Dark for A-Test Women’, and ‘Bomb Survivors are Still Friends’.

Journalists reported with some ill-disguised delight that the women had suffered hallucinations towards the end of their ordeal. ‘Miss Veale thought the sandbags were going to fall on her; Mrs Jones thought people were watching her, and Miss Smith thought she felt objects rushing across her face’, claimed The Times. In the view of the official report, however, ‘the stories about “hallucinations” had very little substance in them’.

For the York Civil Defence Committee, the experiment had been a success – or at least, as they put it, ‘useful’. It had helped test the government’s advice, producing what they viewed as valuable feedback for their superiors at the Home Office, with a generous helping of publicity created in the process. ‘In due course, the Handbook will no doubt be revised’, they confidently wrote.

In reality, the Advising the Householder booklet had been beleaguered from the outset, criticised widely by the media and politicians and even ridiculed in Peter Watkins’ acclaimed (and subsequently banned) BBC documentary The War Game. It would remain the last official government advice on nuclear attack to be made available to the public until 1980, when the Thatcher administration would reluctantly publish a rather better-known and more infamous booklet: Protect and Survive.

Taras Young is the author of Nuclear War in the UK (Four Corners, 2019). He researches and writes about the UK’s Cold War civil defence plans at Communicating the Unthinkable.