In just four years the I-Spy Tribe's numbers swelled to 250,000
I-Spy spotter books, first published in 1949, are being updated and re-released for a new generation of children.
Mansfield head teacher Charles Warrell was the man behind the publishing phenomenon of the 1950s and 60s.
Mr Warrell was a believer in active learning and devised the spotter guides to keep children entertained on long car journeys.
Since its launch in 1949 the I-Spy series has sold over 25 million copies worldwide.
Charles Warrell was the headmaster of Pleasley Hill School, Mansfield, in the 1940s.
He devised his first I-Spy spotter book towards the end of his career in 1948.
"Spotters" gained points for finding the contents of the books in real life situations.
On completion, they sent the books to Big Chief I-Spy, Mr Warrell's alias, for a feather, an order of merit and entry into the I-Spy Tribe.
They were a big hit for children who preferred to use books as a tool rather than reading them from cover to cover.
By 1953 the I-Spy Tribe had half a million members.
The Big Chief
Mr Warrell created and self published the books, having failed to impress no fewer than eight publishers with his idea.
He originally wanted to call the series Learning from Life but was persuaded by his wife Marian to go with I-Spy.
Irene from Arnold, Nottinghamshire, was one of Charles Warrell's pupils at Pleasley Hill School. She said:
"The books made children look around them. If they were on the train they didn't need to ask their dad what something was because they already knew because it would be in their book.
"He was a wonderful headmaster. He loved children but he was also a good disciplinarian."
Stuart, from Sandiacre, Nottinghamshire, found himself on the front cover of the very first edition of I-Spy: At the Airport.
"Dad was going to Northern Ireland with his work for Rolls Royce. We were approached at the airport by a bloke with a camera and he asked my mum if he could borrow us for a while.
"They took us for a drive around the airport on the ramps. They took us to places you couldn't get to. It was super, we really enjoyed it!"
Despite gracing the cover of the 1969 edition, Stuart, who was eight at the time, was not a fan of the books.
"They always seemed to be a Grammar School thing and we were Secondary Modern. Well, we just didn't cut the mustard! They seemed very complicated.
"It was the late 1960s so instead, on long car journeys, we would stare out the windows looking for UFOs which were innumerable on any journey."
New for 2010
Michelin Travel Publications launched 12 new titles of I-Spy in 2009 and a further 12 are due in spring 2010.
Ian Murray, commercial director of Michelin, says that the new books, which include I-Spy Birds, Trees and On a Car Journey are faithful to the original idea but have been updated.
Known affectionately as Big Chief by nursing home staff, Charles Warrell died aged 106 in Matlock, Derbyshire, in November 1995.