Now here come the sons. They are the scions of pop’s most influential and magisterial collaboration. Coursing through the DNA of James McCartney and Sean Ono Lennon are the helix-linked chromosomes of the men whose co-authored songs still permeate and influence the musical landscape.

So the news that the sons of John and Paul had written and released their own first jointly-written song provoked an understandable ripple of interest within the worldwide Beatles community intrigued by the unexpected revival of the famous band collective.

Primrose Hill is a dreamy ballad tinged with a whimsical Beatleseque aesthetic sung by McCartney as a homage to the London suburb where he has long lived. (Trivia note: It’s actually credited to McCartney-Lennon, which must have made James’s old man chuckle.) Lyrically, it also has its roots in Scotland, rekindling those halcyon days he spent on the family farm at High Park on the Mull of Kintyre with Paul, late mum Linda and his sisters Mary and Stella.

McCartney explained the song in an Instagram post: “I had a vision as a child in Scotland, on what was a lovely summer’s day. Letting go, I saw my true love and saviour in my mind’s eye. Primrose Hill is about getting the ball rolling with me and finding this person.”

The Herald: The BeatlesThe Beatles (Image: PA Wire)

However, anyone expecting the song to scale the lofty heights of their famous fathers’ output would be well advised to rein in their expectations. Primrose Hill is a long way from Hey Jude, Let It Be or Strawberry Fields Forever. How could it not be?

In any case, those comparisons are odious and unfair to both men who know they will forever be burdened by the long shadow cast by their family dynasties, particularly Lennon who was just five when his father was gunned down by a deranged “fan” in 1980 outside his New York apartment.

Witness the example of Julian Lennon, John’s son from his first marriage, whose own music career quickly stalled despite the acclaim of his debut album Valotte, leaving him to focus more on philanthropy rather than Billboard.

Meanwhile, George Harrison’s son Dhani has consciously stayed clear of pop’s highway, concentrating instead on film soundtracks and deliberately non-commercial albums. And who could blame them? Fame is a hard horse to ride and the fall can be painful. Ironclad imperviousness to criticism is not a guarantee under the genetic code.

It is likely, therefore, that this new McCartney-Lennon will be a one-off alliance in order to avoid precisely the same kind of media and fan scrutiny both have spent their lives trying to avoid.

Indeed, a reality check is required at this point. Both men are on the cusp of middle age – McCartney is 46 and Lennon is one year shy of turning 50. So neither will be breaking new ground in a terrain currently dominated by Swifties, those in the Beyhive and Harry Styles.

Proof lies in the fact that, by Sunday night, Primrose Hill had been streamed a mere 40,000 times compared to the gazillion Taylor Swift downloads – reportedly 300 million in one day - that threatened to break Spotify.


The Beatles Now and Then review: 'a final love letter to the world'

Ken McNab: John Lennon and Yoko Ono's bed-in protest and the great sell-out

Imagine Lennon hadn't died four decades ago. What would he be doing now?

That, though, is to entirely miss the point. Beatle fans remain – perhaps unhealthily so - preoccupied by the band more than 60 years after they split in 1970 amid a welter of finger-pointing recriminations and internal strife.

Time, of course, has healed all wounds and the surviving octogenarian Fabs – Paul and Ringo Starr – are now perhaps closer than they have ever been – as is the talented extended family of musical Beatle siblings that include Sean, his half-brother Julian, Dhani Harrison and Ringo’s drummer son Zak, who has played and toured with an array of bands including The Who and Oasis.

Lennon’s death ended all hopes of a full-blown Beatles reunion but that has never stopped the clamour from fans speculating about the next generation getting together to form a kind of Beatles Mark Two.

Wisely, no one took the bait – until now. But the times-they-have-indeed changed, although no one is really expecting James McCartney and Sean Lennon to rekindle that old Fab magic.

Nevertheless, it’s intriguing to examine the musical back stories for both men and ask how did they meet at this cross junction after all this time?

Sean Lennon has stubbornly refused to plough a familiar pop music furrow. Indeed, his musical explorations have largely more mirrored the avant-garde tastes of his mother Yoko Ono. A talented songwriter, musician, producer and filmmaker, Lennon has worked with a diverse range of collaborators, notably Les Claypool, Moby and Rufus Wainright. He also formed the highly-acclaimed band The Ghost of a Sabre Tooth Tiger with long-term partner Charlotte Kemp Muhl. His most commercial offering was the 2006 album Friendly Fire, which crashed the Billboard Top Ten.

In March, he accepted the Academy Award for Best Animated Short Film, War Is Over!, inspired by the music of John and Yoko. As part of his speech, Ono Lennon led the Awards’ audience in wishing his mother “Happy Mother’s Day, Yoko!”

Looking and sounding eerily like his dad, Lennon’s determination to carve out his own career identity says much about a man who has long come to terms with the fateful burden of carrying a famous surname.

The same, unfortunately, cannot be said for James for whom the family sobriquet was a crown that clearly weighed too heavily.

He began releasing his own music with a 2010 EP titled Available Light, which he recorded partly at Abbey Road. His first full album, Me, from 2013, was produced by David Kahne, a former record executive who has worked with the Strokes, Linkin Park, Lana Del Rey and yes, Paul McCartney. Its follow-up, The Blackberry Train, came out in 2016. James previously contributed fine guitar to his father’s 1997 album Flaming Pie.

Since then, however, he has mainly flown below the radar, shunning the publicity and chat show merry go-round that is often a necessary evil for artists to promote their work, knowing that most interviewers will be more fixated on what it was like growing up with a Beatle at the family dinner table.

And there is no sign that he’s about to break the habit of a lifetime by breaking cover to support his latest offering.

Indeed, his public utterances have so far been restricted to ‘thanking my good friend Sean Lennon” while adding: “With the release of this song it feels like we’re really getting the ball rolling and I am so excited to continue to share music with you.”

The Herald: Sean LennonSean Lennon (Image: free)

Typically, there was no shortage of keyboard warriors lining up inside the Internet echo chamber to take anonymous pot shots at a collaboration between two friends who are clearly in it for the fun, knowing there will always be the comfort of daddy’s financial legacy to fall back on if it all goes pear-shaped.

Indeed, one observer ruefully commented on McCartney’s latest song in an Instagram post: "Sad you can’t just walk your own road.”

It was left to Ringo's son Zak Starkey, now 58 years of age, to underline a new Beatle musketeer mantra of having each other’s back – just as their fathers did in the Sixties.

Starkey replied: “The Beatles are a wall you cannot go through, over or under — I was 25 when I came to terms with that.”

Who knows? Maybe there is still time for them to come together from across the Beatle universe and surprise us all. Imagine that.

Ken McNab is a lifelong Beatles fan and the author of The Beatles in Scotland and And in the End: The Last Days of The Beatles.