During an 18-month separation from Yoko Ono, Lennon reached musical highs as well as personal lows.

To label a period of 18 months a “lost weekend” seems a stretch to many, but to John Lennon it marked a time of intense creativity, outrageous behavior, a musical reunion with Paul McCartney, and the breakup and reconciliation of his relationship with Yoko Ono.

Lennon took the moniker for this period of self-introspection and productivity from The Lost Weekend, a 1945 film starring Ray Milland as an alcoholic writer struggling to overcome his addiction and return to his creative process.

Lennon began an affair with May Pang

Beginning the summer of 1973 and lasting through early 1975, Lennon’s lost weekend marks the period of separation between himself and  Ono. Four years into their marriage the cracks were beginning to show and Lennon moved out, embarking on an affair with the couple’s assistant May Pang. Lennon and Pang split their time between Pang’s New York City apartment and a house they rented in Los Angeles.

Pang has always maintained the relationship happened with Ono’s blessing. “The affair was not something that was hurtful to me,” Ono told The Telegraph in 2012. “I needed a rest. I needed space. Can you imagine every day of getting this vibration from people of hate? You want to get out of that,” she added in reference to many fan’s belief she was instrumental in breaking up The Beatles. “I started to notice that he became a little restless on top of that, so I thought it’s better to give him a rest and me a rest. May Pang was a very intelligent, attractive woman and extremely efficient. I thought they’d be OK.”

John Lennon and May Pang

John Lennon and girlfriend May Pang at the Beacon Theatre for 'SGT. Pepper's Lonely Hearts Club Band on the Road' on November 17, 1974, in New York City

Lennon drank alcohol and did drugs in excess

Away from Ono, Lennon began drinking heavily and abusing drugs. In L.A., he teamed with producer Phil Spector to record an album of rock standards that had inspired him. “The guys were all drinking — and John was being one of the guys,” Pang said to Uncut in 2009. “Everyone was as blitzed as he. One of the bass players got into a car wreck. We got kicked out of A&M [studios] when someone threw a bottle of liquor down the console.”

A more famous ejection happened when Lennon and his drinking buddy, singer-songwriter Harry Nilsson, were tossed out of the Troubadour rock club in West Hollywood in March 1974 for heckling the Smothers Brothers. “I got drunk and shouted,” Lennon reportedly recalled of the incident. “It was my first night on Brandy Alexanders — that’s brandy and milk, folks. I was with Harry Nilsson, who didn’t get as much [press] coverage as me, the bum. He encouraged me. I usually have someone there who says, ‘OK, Lennon. Shut up.’”

Harry Nilsson and John Lennon

Harry Nilsson and John Lennon being thrown out of the Troubadour club in West Hollywood, California on March 12, 1974

He reunited with Paul McCartney for a jam session

Despite the substance abuse, the period was a productive time in regards to music. Lennon completed three albums, Mind Games, Walls and Bridges and Rock ‘n’ Roll, as well as producing LP’s for Nilsson and former bandmate Ringo Starr. Surprisingly, the single “Whatever Gets You Through the Night,” from Walls and Bridges, was Lennon’s first solo number one hit in the U.S., featuring Elton John on piano and backing vocals.

But it was an impromptu jam session on March 28, 1974, that ignited rumors of a possible Beatles comeback. Lennon was at Burbank Studios producing a single for Nilsson when McCartney and his wife Linda unexpectedly stopped by. “I jammed with Paul,” Lennon revealed in a later interview. “I did actually play with Paul. We did a lot of stuff in L.A., though there were 50 other people playing, all just watching me and Paul.”

The session is the only known instance of Lennon and McCartney playing together between the breakup of The Beatles in 1970 and Lennon’s murder in 1980. The tape of the session was released on the bootleg A Toot and a Snore in ‘74 but produced nothing musically substantial.

A subsequent reunion between the two was reportedly being discussed, with Lennon planning to meet McCartney in New Orleans where the latter, along with his band Wings, would be recording the album Venus and Mars in early 1975. In her memoir, Pang wrote that Lennon was open to the notion. “He kept bringing up the trip, and each time he mentioned it he grew more enthusiastic,” she says in Loving John: The Untold Story.

John Lennon Lost Weekend

John Lennon with May Pang and Harry Nilsson (right) at the Troubadour on March 12, 1974, in West Hollywood, California

Lennon eventually reunited with Yoko Ono and went on to have a son with her

But the anticipated meeting in New Orleans would never come to pass. Around the same time, Ono had reached out to Lennon requesting he visit their apartment at The Dakota in New York regarding a treatment she thought would end his nicotine addiction. Lennon, who said he spoke with Ono almost daily during his “lost weekend” and begged to be allowed to return home, would remain with his wife from then on. Their son Sean would be born in October 1975.

Explaining their decision to reunite, Ono told Playboy in a joint interview with Lennon in 1980 that it, “slowly started to dawn on me that John was not the trouble at all. John was a fine person. It was society that had become too much. We laugh about it now, but we started dating again. I wanted to be sure. I’m thankful for John’s intelligence… that he was intelligent enough to know this was the only way that we could save our marriage, not because we didn’t love each other but because it was getting too much for me.”

For Lennon, it was about reordering priorities with the focus now being on the family. Especially with a new baby on the way. “The number one priority is her and the family,” he told Playboy. “Everything else revolved around that.”

Taking on the role of househusband, Lennon focused on family and took a five-year hiatus from the music industry. In October 1980 he released the single “(Just Like) Starting Over,” ahead of the November release of his and Ono’s album Double Fantasy which received mostly negative critiques. It would be Lennon’s last studio album before his death the following month.

Pang would remain in contact with Lennon until his death. She married record producer Tony Visconti in 1989 and the couple had two children. They divorced in 2000. In a 2015 interview, Pang referred to her split with Lennon, the end of the “lost weekend,” as a “gray zone.” She recalled that at that time, early 1975, the couple were considering buying a home in the Hamptons, and then Lennon returned to Ono. Pang said she remained romantically involved with Lennon for several years after their split and the last time she saw him was the winter of 1978-1979.