First Men in the Moon (1964)

In present day, an international team, to great worldwide fanfare in the accomplishment, has just landed on the moon, the first time humans have both landed and stepped foot on the satellite. The astronauts/cosmonauts, however, make an unusual discovery on the moon's surface: a Union Jack and a summons issued to a Katherine Callender of Dymchurch, England dated 1899. Upon investigation, the UN Space Agency does discover that a Katherine Callender of Dymchurch did exist, has since passed away, but married a Arnold Bedford who is still alive and residing in an area nursing home. At the nursing home, the matron states that Bedford is prone to delusions, but when the team speaks to Bedford directly, he tells them a story that may sound delusional to the uninformed but makes sense as to the moon finding. An aspiring playwright deep in debt at the time, Bedford tells of how he and Kate, not yet married, met their eccentric neighbor, scientist Joseph Cavor, and how that meeting led to the three of them making an expedition to the moon, complete with how they made it there. With their misadventures and his worries for the current expedition team as to his and his compatriots' experience, Bedford completes the story with what happened to Cavor at the time (with Kate's fate already known) and why the world never knew of their moon landing.