Paul McCartney first spotted John Lennon on a bus — and that encounter made an unmistakable impression on the artist.

“I’d seen him a couple of times and thought, ‘Wow, you know, he’s an interesting'looking guy,” the 78-year-old told Lennon’s youngest son, Sean Ono Lennon, during a BBC Radio 2 special commemorating what would have been the singer/songwriter’s 80th’s birthday.

“And then I once also saw him in a queue for fish and chips and I said, ‘Oh, that’s that guy off the bus,” McCartney continued. “I’m talking to myself, in my mind I thought, ‘I saw that guy off the fbus, oh he’s pretty cool-looking. Yeah, you know, he’s a cool guy.’”

McCartney shared the two were just teens at the time and had a shared interest in the ‘50s “Teddy Boy” fashion, which includes slicked-back hair, drainpipe trousers and long jackets.

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1st November 1963:  Two members of Liverpudlian pop group The Beatles, John Lennon (1940 - 1980), singer and guitarist, left, and Paul McCartney, singer and bass guitarist.  (Photo by Fox Photos/Getty Images)

John Lennon (1940 - 1980), singer and guitarist, left, and Paul McCartney, singer and bass guitarist, circa 1963. (Fox Photos/Getty Images)

“I knew nothing about him except that he looked pretty cool,” said McCartney about his future music collaborator. “He had long sideboards and greased back hair and everything… it was the Teddy Boy look. All of us were trying to do a bit of that at that point, so if you ever noticed someone who was trying to do it you thought, ‘I’ll probably get on well with him.’”

“But I didn’t know anything about him,” noted McCartney. “And I didn’t know who he was except that I’d seen him on the bus and I’d seen him in the fish and chip shop.”

A mutual friend named Ivan would eventually introduce Lennon to McCartney at a church fair on July 6, 1957, People magazine reported on Tuesday. At the time, Lennon was performing with a band called The Quarrymen.

The outlet revealed that a friendship blossomed between the two, and Lennon would regularly visit McCartney’s house to learn chords and practice.

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John Lennon, Paul McCartney, George Harrison and Ringo Starr.

John Lennon, Paul McCartney, George Harrison and Ringo Starr. (Richard Parkin Starkey. Mondadori via Getty Images)

While both hailed from Liverpool, McCartney said their upbringings were vastly different. McCartney came from a large, friendly, music-playing family. Lennon, on the other hand, was removed from his mother at age 5 to live with his aunt.

“It was only later when I realized… what a difficult upbringing he’d had compared to me,” said McCartney, adding Lennon “idolized” his mother.

“It was so sad that he wasn’t living with her and his half-sisters,” he added.

McCartney and Lennon, as well as fellow bandmates George Harrison and Ringo Starr, had no formal musical training. But McCartney said that only forced The Beatles to learn how to write, play and record music together.

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Sir Paul McCartney at Waterstones Piccadilly on Sept. 6, 2019, in London, England.

Sir Paul McCartney at Waterstones Piccadilly on Sept. 6, 2019, in London, England. (Mike Marsland/WireImage/Getty Images)

“I look back on it now like a fan,” said McCartney. “I think, ‘Wow. How lucky was I to meet this strange Teddy Boy off the bus who turned out to play music like I did, and we get together and, boy, we complemented each other.’ You know, it was a bit yin-yang.”