The best Carpool Karaoke yet: James Corden and former Beatle Sir Paul McCartney in Liverpool

James Corden and Sir Paul McCartney.

Talk show host James Corden brought Sir Paul McCartney back to the streets and pubs of Liverpool for what may be the best — and certainly most emotional — Carpool Karaoke segment ever.

The Late Late Show host teared up after Sir Paul related the story behind one of the last big Beatles hits, Let It Be, revealing that he wrote it after a dream of his mother, who had died when he was 14.

Paul McCartney Carpool Karaoke

James Corden heads to Liverpool for a special day with Paul McCartney spent exploring the city of Paul's youth, visiting his childhood home where he wrote music with John Lennon, performing songs in a local pub and of course driving around singing a few of Paul's biggest hits. Pre-order Paul McCartney's new album Egypt Station and download his two new songs “Come On To Me” and “I Don’t Know” here: https://paulmccartney.lnk.to/EgyptStation Watch The Late Late Show with James Corden's episodes from London only on Sky One at 10pm.

Posted by The Late Late Show with James Corden on Friday, 22 June 2018

Visibly moved after singing, Corden said: "It got me emotional there Paul, I didn't see it coming, it's too much for me."

"That's the power of music, how that can do that to you," the rocker, who turned 76 last Monday, said in reply.

The 23-minute segment proved emotional for Sir Paul, too, as the two visited the Penny Lane barbershop immortalised in the song of that same name, the house where he lived as a teenager, and a pub where he and John Lennon performed.

In his old house at 20 Forthlin Rd in the Liverpool suburb of Allerton, Sir Paul showed where he and Lennon rehearsed, and revealed that his father offered some pointed criticism when the duo played him their song She Loves You.

"There's enough of these Americanisms around. Couldn't you sing 'She loves you, yes yes yes?" he said.

The segment ended with Sir Paul fronting a surprise gig at the Philharmonic Dining Rooms, where he ripped through a set of Beatles hits, including A Hard Day's Night, Oh-Bla-Di Oh-Bla-Da, Love Me Do and Back in the USSR before welcoming Corden on stage for an encore of Hey Jude.

The segment quickly gained praise online, with Twitter users describing it as "one of the all-time great TV moments" and "the coolest thing to happen on a late night show since a certain band appeared on ED SULLIVAN in February of 1964 — just awesome".