Bob Dylan and Neil Young co-headlined a UK gig for the first time as the sun set over London's Hyde Park on Friday.
"I've never played in daylight before!" joked Young, who went on stage first, adding: "It's great to see everybody."
The event, which was originally billed as part of the Barclaycard presents BST series, went ahead as a solo concert without any sponsorship.
That's after he refused to perform at a festival bearing the name of what he called "a fossil fuel-funding entity".
On site, fans applauded the Canadian's decision to pull rank in order to make an environmental point. One fan told the BBC: "If an old rocker wants to pull his weight and knock some people around in the corporate world that's good, why not?"
Another agreed, saying: "If that's what he promotes and he's against that, then they are the people that need to do it - the people with a platform."
"That's the way forward, we need to be greener," added a third fan.
However, they all said they would not have supported the gig being pulled completely for the same reason.
"We might have got a refund at least!"
Young - one of the original Woodstock hippy stars - strolled out on stage with a smile and strapped on his battered old black Les Paul guitar. The guitar strap itself was adorned in Ban the Bomb logos, as a peace dove (which turned out to be a descending keyboard) hovered above his head and a Love sign was displayed near his amp.
The historic first coming together of two of rock's biggest protest singers on British soil occurred on the same day that many other similarly politically green-minded music stars, including Radiohead, Foals and Hot Chip, called on the government to take action over climate change.
The 73-year-old was forced to scrap a string of UK gigs back in 2013 due to an injury to one of his Crazy Horse bandmates, but this time around he was backed by The Promise of the Real, featuring Willie Nelson's son Lukas.
Their tight-knit rhythmic jamming allowed the guitarist to show he can still cut loose on old favourites including Everybody Knows This Is Nowhere and Alabama - which was perceived as a 'diss' track by US southern rockers Lynyrd Skynyrd, who responded to Young directly in the lyrics to their 1973 hit, Sweet Home Alabama.
There were loud cheers all around when the acoustic guitar and harmonica came out for a rendition of Heart of Gold. The singer-songwriter confirmed late last year that his search for one of those was indeed over after having married actress Daryl Hannah.
The first half of the big night ended with the extended wig-out of Rockin' in the Free World, before Young and his band returned for an encore which included a hypnotic and tremolo-soaked Like a Hurricane - the highlight of his set.
His signature tune, Hey Hey, My My (Into the Black), was sadly notable by its absence.
Young and his hero Dylan had played on-stage together previously in 1992 - alongside George Harrison and Eric Clapton - at a New York gig to mark 30 years of the American's music, and before that at their friends The Band's last-ever gig in 1976, which was captured on film by Martin Scorsese in The Last Waltz.
Whispers murmured around Hype Park that it could happen again during Dylan's set, but alas, it was not to be.
As anyone who saw Scorsese's recent semi-fictional Dylan tour film, Rolling Thunder Revue, will testify, the 10-time Grammy winner has been keeping fans and band members alike on their toes his whole career and this gig was no different.
Dylan walked on unannounced, sat down at the piano with a grin and burst straight into Ballad of a Thin Man from his seminal 1965 album, Highway 61 Revisited.
While Young had ripped through a set of largely record-faithful live versions of his tracks, Dylan - who appears to no longer play the guitar - reworked many of his hits in different styles, keys and with different melodies. Part of the fun and challenge of seeing him perform in 2019 is picking out the correct tune before your neighbour does, as I somehow managed on the early bar-room version of It Ain't Me, Babe.
All of this prevented any real mass sing-alongs from breaking out early on as the crowd - which included Jarvis Cocker and Jake Bugg - watched a delighted Dylan re-paint his masterpieces live, getting up on his feet several times to strike some Elvis Presley-esque hip-shaking poses centre stage. But by the start of his mid-set classic Like a Rolling Stone most punters had gained the confidence to belt out the song's original vocal melody together in harmony like a giant choir backing the singer's off-kilter delivery.
These days, the 78-year-old's deeper voice seems to suit the blues-ier numbers - like the song Highway 61 Revisited - more than the folk ballads, although his heartfelt efforts on Simple Twist of Fate, Girl from the North Country and To Make You Feel My Love reminded us all why local London lovesick song specialist Adele chose to cover him so committedly.
Dylan's on-stage patter is non-existent now, but one thing that remains undiminished is his ability to play the harmonica, and while some of best-loved songs - including Mr Tambourine Man, Forever Young and Don't Think Twice - were omitted, such is his arsenal it would have been impossible to send everybody (himself included) home happy.
After a long day of music in the sun, large sections of the crowd began to lose interest as Dylan embarked on a hat-trick of later career tunes, although he soon won them back with an upbeat You've Gotta Serve Somebody, followed by an encore of an intriguing Blowin' in the Wind and the brilliantly-titled It Takes a Lot to Laugh, It Takes a Train to Cry.
Dylan's late Travelling Wilburys buddy Tom Petty played his last-ever UK gig on the same stage two years earlier and despite widespread issues with sound blowing in the wind at festivals this summer, Hyde Park seem to have really nailed their outdoor sound system for big nights like these.
Barclaycard resumes its Hyde Park summertime takeover this weekend with performances from Florence + the Machine, The National and Robbie Williams. Let's just hope they wait until Neil Young is off site and on the peace trail elsewhere before those posters go back up.