Stills from John Lennon Home Movie 1968

To say that Yoko Ono had a profound effect on John Lennon and the Beatles is an understatement. Her first exhibition in London was at the Indica Gallery, a trendy shop frequented by the Beatles and originally started with the backing of Peter Asher, brother of Paul's girlfriend Jane. John visited Indica on November 7, 1966. He climbed a ladder to view the word "yes" through a magnifying glass tied to a string and hanging from the ceiling. He would later say that this particular exhibit caught his attention because the word was positive.
Most accounts agree that, following John's meeting with the performance artist, Yoko did everything possible to be in the company of John, such as forcing her way into Abbey Road Studios or standing outside with young female fans called Apple Scruffs. Yoko also climbed into the backseat of John's limousine, placing herself between Lennon and his wife Cynthia. She also sent John frequent notes and small packages containing her art.
After John and his wife returned from India, Cynthia Lennon was urged by John to go on holiday. She traveled to Greece with Magic Alex and Jenny Boyd, older sister of George's wife Patti. Shortly thereafter, John invited Yoko to his house at Kenwood. It was during this visit that John and Yoko went to the attic studio, dropped acid, and recorded electronic shrieks and noises eventually released as the album Two Virgins. Cynthia returned from her trip to find John and Yoko sitting in bathrobes on the floor of the Kenwood sunroom. Cynthia filed for divorce on August 22, 1968, upon learning that Ono was pregnant by John.
Yoko began attending Beatles' recording sessions during The White Album. She became a constant companion to John and can be seen sitting by his side for most of the Let It Be sessions. To the other Beatles, this was highly unorthodox since Beatle sessions were always closed except to guest performers Eric Clapton ("While My Guitar Gently Weeps") and Billy Preston ("Get Back"). Later, in June of 1969, John had a bed brought into Abbey Road Studios so that while the group recorded, Yoko could recuperate from injuries sustained in an automobile accident.
John and Yoko were married on March 20, 1969, and spent their honeymoon in Amsterdam, staging their first "bed-in." Subsequently, the couple combined political activism with performance art, such as "bagism." They moved to New York in 1971, ultimately settling into the Dakota in 1975. Beginning in June of 1973, John and Yoko separated for eighteen months, with John living in Los Angeles, a period known as John's "Lost Weekend" since his drunken and disorderly conduct was widely reported by the mainstream media while he partied and lived with Ono-ally May Pang. John and Yoko reconciled in January 1975. Yoko is often blamed for breaking up the Beatles, although this is a gross simplification. Tension within the group had run high ever since the death of Beatles' manager Brian Epstein left a gap in the band's leadership, unofficially assumed by Paul. George and Ringo also left the group for short periods of time before reuniting temporarily to record the group's final album, Abbey Road. The consensus of most biographers is that John, George, and Ringo all felt quite aggravated at Paul McCartney's overbearing manner during the final years of the group as he attempted to provide direction for the band after Brian's death. John felt that he, George, and Ringo were becoming a back-up band for Paul.
For the interested reader, details about John and Yoko's relationship can be found in Cynthia Lennon's John (2005), a book that reveals much of John's life in detail for the first time from Cynthia's perspective.