On June 25, 1967 — at the start of what came to be known as “The Summer of Love” — the world’s most popular and revolutionary rock band, The Beatles, debuted their newest song in front of a global television audience estimated at 400 million people. The Beatles appeared at the end of a broadcast titled Our World, the first time that satellites were used to beam a single TV broadcast around the world.

Watch video of the historic broadcast with The Beatles performing the now-classic number below on this page.

The song not only defined the “Summer of Love,” but went on to become an iconic anthem of unity and love that is played and performed frequently to this day. Written primarily by John Lennon, the song was titled “All You Need Is Love.”

But when The Beatles, who were then finishing the recording of their album Sgt. Pepper’s Lonely Hearts Club Band, were told about a month earlier by their manager Brian Epstein that they would be included in the world’s first global TV broadcast, the Fab Four — Lennon, Paul McCartney, George Harrison and Ringo Starr — were less than enthused.

“Ringo fidgeted at the back of the room,” wrote Beatles recording engineer Geoff Emerick in his 2006 memoir, Here, There and Everywhere: My Life Recording the Music of the Beatles. “George resumed tuning his guitar. John and Paul exchanged blank looks for a moment. With a distinct lack of enthusiasm, John finally said, ‘Oh, okay, I’ll do something for that.’”

The Beatles went on the air live to 24 countries from Studio Two at Abbey Road recording studios in London, England, at 9:36 p.m. Greenwich Mean Time, which would have been 5:36 p.m. Eastern Time in the United States. Watch video of the landmark performance, which was originally carried in black-and-white, below.

The Beatles performance was carefully prepared, with live elements played by the band over a backing track that had been recorded 11 days earlier. In fact, the band on June 14 had recorded 33 separate takes of “All You Need Is Love” under the supervision of their longtime producer George Martin, choosing the 10th take as their favorite and the version they would use in the Our World broadcast.

When the Beatles played the song for a worldwide audience on five continents, however, Lennon’s vocals, Starr’s drums, McCartney’s bass guitar and a lead guitar solo played by Harrison were all live — as was the instrumentation played by a 13-piece orchestra of classical musicians.

“‘All You Need Is Love’ was John’s song. I threw in a few ideas, as did the other members of the group, but it was largely ad libs like singing ‘She Loves You’ or ‘Greensleeves’ or silly things at the end and we made those up on the spot,” McCartney remembered 30 years after the broadcast, interviewed for Barry Miles’ book, Many Years From Now.

“The chorus, ‘All you need is love,’ is simple, but the verse is quite complex. In fact, I never really understood it. The message is rather complex. It was a good song that we had handy that had an anthemic chorus.”

The Beatles invited many of their friends — other top British rock stars of the 1960s — to appear in the worldwide broadcast. Among the luminaries who can be spotted in the above video: Mick Jagger and Keith Richards of The Rolling Stones, Jagger’s then-girlfriend singer Marianne Faithful, Keith Moon of The Who and guitarist Eric Clapton. McCartney’s then-girlfriend actress Jane Asher appears in the video, as does Harrison’s wife at the time, Patty Boyd.

John Lennon, the lead singer and primary songwriter of “All You Need Is Love” died in 1980 at age 40 when he was gunned down by a “crazed fan” outside his New York City apartment building. George Harrison passed away at age 58 of cancer. McCartney and Starr, however, continue to record and perform around the world today. McCartney is 75 years old, while Starr — whose real name is Richard Starkey — will turn 77 on July 7 of this year.

[Featured Image by BIPS/Getty Images]