Tony Essex, who worked for Midland Bank, recorded footage of the Queen Mother at the show in 1964
About 100,000 people are expected to attend the 160th and final Royal Show in Warwickshire.
The agricultural event in Stoneleigh is being cancelled after this year because of falling visitor numbers.
During its heyday in the 1970s and 1980s about 250,000 people would regularly attend.
The Royal Agricultural Society of England (Rase) said in April the event was no longer financially viable and would not continue in its present form.
Poor weather and outbreaks of foot-and-mouth and bluetongue - which restricted the number of livestock on show - have contributed to its problems in recent years.
The final show - which lasts until Friday began with a pageant paying tribute to its history before the action gets under way in the Grand Ring.
In its heyday the show attracted 250,000 people
Denis Chamberlain, Rase's marketing director, said he was determined to "give everyone a great show".
The first show, in 1839, was held in Oxford and subsequently also in Liverpool and Manchester.
It has taken place each year since, with the exception of during World War I and World War II and when there were outbreaks of cattle plague and foot-and-mouth disease.
The show has been held at Stoneleigh Park since 1963.
Rase said it was instead planning to hold a series of year-round events which would retain key elements of the Royal Show.