This, we are told, was the day John Lennon decided to quit The Beatles.

As recently as four days ago, according to Mark Lewisohn, he had been pushing ideas for the next single and album. So what happened? One possibility is that he wanted the single to be “Cold Turkey” and the others scuttled that idea, perhaps feeling that a hard-edged screed about heroin withdrawal was not commercially viable. (As it happens, “Cold Turkey” — when recorded by the Plastic Ono Band — reached the top 20 in the UK and the top 30 in both the U.S. and Canada.)

I imagine John being in a pissed-off mood, again feeling creatively stifled by his bandmates — and already back on heroin, by the way — when a fateful phone call arrived from Toronto today. According to The Beatles Bible,

Live music promotor John Brower telephoned the Apple office and spoke to John Lennon, inviting him and Yoko Ono to the Toronto Rock and Roll Revival festival taking place the following day.

Brower offered eight first class tickets for the couple and their friends. At the time sales for the festival were slow, and he needed some high profile guests to boost its appeal.

To his surprise, Lennon agreed on the condition that he could perform at the event.

And just like that, John made a snap decision to put together a band that would perform in Canada the following day. He asked George to come along, but George was not into it; so just as he’d thought about doing during the Get Back/Let It Be sessions, John got Eric Clapton to take George’s place. He also recruited old friend Klaus Voormann to play bass and a drummer named Alan White, and they all planned to meet the next morning for the flight to Toronto.

It was on this flight, legend has it, that John told Allen Klein he was quitting the band; the rest of The Beatles would find out a week later. But that’s tomorrow — for today, I’m guessing, John took a fix and went on the nod.