Samuel Shenton was a signwriter, who lived with his wife Lillian in a ginger-brick terrace in suburban Dover. He was son of an army sergeant major, born in Great Yarmouth, and by the 1920s claimed to have invented an airship that would rise into the atmosphere and remain stationary until the earth spun westwards at 1,000 km/h (620 mph) to the desired destination at the same latitude. Shenton could not understand why someone had not previously thought of this idea until he discovered, in the reading room of the British Library at Bloomsbury that Archbishop Stevens, a friend of Lady Blount, the founder of the Universal Zetetic Society, had suggested an aircraft design similar to his own. When he discovered Parallax's Zetetic Astronomy he was an instant convert. "What the authorities were concealing, Shenton decided, was the 'fact' that the earth was flat".
Shenton soon constructed a cosmology, based partly on his interpretation of Genesis, that the earth was a flat disk centred on the North Pole with the zetetic notion of the South Pole being an impenetrable wall of ice, that marked the edge of the pit that is the earth in the endless flat plane forming the universe. The sun cast a narrow beam like a flashlight moving over a table as it traced flat circles that varied over the 365-day cycles. The sun was 32 miles (51 km) in diameter 3,000 miles (4,800 km) above the earth and the moon also 32 miles in diameter but only 2,550 miles (4,100 km) above the earth.
In 1956 he founded the International Flat Earth Research Society as a direct descendant of the Universal Zetetic Society but with a less religious emphasis, found a president in William Mills, a relative of one of Lady Blount's followers and held its inaugural meeting in November at Mills' home in London, with Shenton as secretary. One of the attendees, attending out of curiosity, was the Sky at Night astronomer Patrick Moore who recounted his experience in his book Can you speak Venusian?.
Despite the launch in October 1957 of Sputnik, the world's first artificial satellite, Shenton proved a popular speaker to small groups, enjoying particularly talking to children, never declining an invitation. He claimed that satellites simply circled over a flat disc-world: "Would sailing round the Isle of Wight prove that it were spherical?", he demanded. As manned space flight started in 1961, Shenton began to attract international media attention with his denials, telling the Coshocton Tribune on 10 May that the astronauts could never travel into orbit.
When John Glenn orbited the world, he was sent an IFERS membership with the message "Ok Wise Guy" added to it. Shenton continued to lecture largely at his own expense but he suffered two strokes in 1963 probably as a result of his exertions. In January 1964 the New York Times carried a piece about the IFERS. During a parliamentary debate, Enoch Powell likened his opponents to "flat-earthers" and Harold Wilson reportedly slung back the insult in turn. Shenton was outraged and wrote letters of complaint.
The Gemini 4 mission marked a change of pace for his campaign and he was to receive letters from across the world for the next few years. In 1966 he produced a pamphlet, The Plane Truth, which included a circular informing members "that modern astronomy and space flight were insults to God and divine punishment for humankind's arrogance was a mere matter of time". But the Lunar Orbiter program led to a sharp decline in membership. "Visual images, whether they were globes, photographs or television pictures, were clearly critical to how people perceived the earth's shape .. and pre-school children could know that it was round even if they had no grasp of the words 'mathematics', 'geography', 'astronomy' and 'science'".
By 1968, his health had deteriorated further and his signwriting business had collapsed although the media attention continued. But he stuck to his principles of 'zetetic enquiry' in which only personally acquired facts were permissible. In 1969, he found the successor he had been looking for: Ellis Hillman, a lecturer and member of the Greater London Council, agreed to be president of the IFERS, with the encouragement of Patrick Moore. Lillian Shenton was suspicious of his motives (he was developing a post-graduate course on the development of ideas about the shape of the earth) and in the event he did little for the society. Eighteen months later, Shenton had died.