On January 30, 1969, at lunch time, The Beatles appeared on the rooftop of their record label’s headquarters, unannounced, and started performing. Londoners looked on with excitement and bafflement as the world’s biggest band, which hadn’t played live in two and a half years, tried out new material for 42 minutes. It would end up being their final live show.

Here are 10 things you might not have known about this strange moment in pop culture.

1. The concert took place during the Beatles’s “winter of discontent.”

When The Beatles reconvened in January of 1969, the band was frayed and dysfunctional, according to The Beatles: Ten Years That Shook the World, Mojo magazine’s book-length chronicle of the group. Paul McCartney assumed leadership of the band and envisioned the follow-up to the White Album, tentatively titled "Get Back," as a return to basics. The band would write songs and bang them out as a four-piece ensemble, forsaking all the overdubs and lavish production of their past few albums.

George Harrison came to resent McCartney's control, and recordings were often interrupted as the two bickered over Harrison’s guitar work. Ringo Starr was anxious for the project to end so as to not conflict with the filming of The Magic Christian, a comedy in which he was slated to star alongside Peter Sellers. John Lennon was prone to long silences, allowing the ever-present Yoko Ono to speak for him. Harrison and Lennon reportedly came to blows over the Yoko issue, a report the former denied to the press. Harrison called the time “the winter of discontent” and Lennon dubbed the Get Back effort “the most miserable sessions on Earth.” The recordings were scrapped in favor of Abbey Road and then retooled as Let It Be, The Beatles’s final album.

2. The concert was staged for a TV project.

McCartney planned a two-night TV special to accompany the release of Get Back. The first installment would document the group writing the material and the second would show them performing it live, marking their first concert since their 1966 U.S. tour. The band’s press agent, Derek Taylor, even told the media The Beatles were scouting locations for a January 18, 1969, concert, according to Ten Years That Shook the World. The band hired director Michael Lindsay-Hogg, who had created a handful of their promotional videos (including those for “Paperback Writer” and “Hey Jude”). Like the album, the TV special did not pan out as envisioned. In 1970, Lindsay-Hogg’s footage became a documentary film, also titled Let It Be.

3. The Beatles picked the rooftop for one main reason: convenience.

In The Beatles Anthology coffee table book, Neil Aspinall, the band’s former road manager and head of their label Apple Corps, said he suggested a boat, a Greek amphitheater, and London venue the Roundhouse as locations for the live show. But scheduling didn’t allow for any of those. “[I]t was a case of, ‘How are we going to finish this in two weeks’ time?’” McCartney recalled in Anthology. “So it was suggested that we go up on the roof and do a concert there. Then we could all go home. I’m not sure who suggested it. I could say it seems like one of my half-baked ideas but I’m not sure.”

4. Billy Preston was hired to lighten the mood.

Keyboardist Billy Preston, a distinguished American session musician, is the only non-Beatle in the rooftop performance. The band met him in their early 1960s Hamburg days and thought he could lighten the mood in 1969. “He got on the electric piano and straightaway there was a 100-percent improvement in the vibe in the room,” Harrison said in Ten Years That Shook the World.

5. There’s a reason no George Harrison songs were played.

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Five new songs were played in a total of nine takes. All of the songs—“Get Back,” “Don’t Let Me Down," “I’ve Got a Feeling,” “One After 909,” and “Dig a Pony”—were credited to Lennon and McCartney. Harrison contributed a few songs to the Get Back sessions, including an early version of “My Sweet Lord.” According to Ten Years That Shook the World, the band skipped them because they didn’t know if he would still be a Beatle when the project was done. The guitarist walked out of the Get Back recordings twice, at one point telling the band they should advertise for his replacement in the British music magazine NME.

6. The concert's audio was piped to the basement.

As the band played, the audio feed went to producer Alan Parsons in the basement of the building.

7. There were cameras hidden at street level.

Lindsay-Hogg’s camera crew set up cameras in the windows of the Apple Corps building that morning, anticipating a crowd gathering.

8. Onlookers were underwhelmed by the Beatles's performance.

As the band played, traffic came to a halt, pedestrians gathered around the Apple Corps building, and workers in neighboring buildings came to their windows and their own roofs. “I remember it was cold and windy and damp,” Starr said in Anthology, “but all the people looking out from the offices were really enjoying it.”

Contemporary assessments, gathered in Ten Years That Shook the World, were more critical. “It’s The Beatles? Christ, it doesn’t sound like that,” said one man. “You call that a public performance? I can’t see them,” complained a woman. “This kind of music is alright in its place, but I think it’s a bit of an imposition to disrupt the business in this area,” said an annoyed Londoner.

9. Some Apple Corps employees skipped the concert to keep working.

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“I knew there was going to be something on the roof but it was not my business,” press agent Derek Taylor said in Anthology. “I had other things going on and saw people outside in the street.” The band’s longtime producer, George Martin, was also in the building. “I was downstairs when they played on the roof,” he said, “worrying like mad if I was going to end up in Saville Row police station for disturbing the peace.”

10. Police pulled the plug on the concert—literally.

Eventually, a bank manager (no doubt London’s biggest square) called police to complain about the noise. Officers from the Greater Westminster Council marched over to Apple Corps and made their way up to the roof. In Anthology, McCartney claims he heard an officer yell, “You have to stop!” (he said he still remembered his badge number: 503), but the singer egged the band on to continue until the officer yanked a cord from the equipment setup, ending the performance. No one, Beatle or otherwise, was charged for the incident.