YOU really don’t have to know Sean, to realise what his surname is.

For the first 10 minutes of our meeting, I sit slightly open-mouthed at the astounding resemblance to his dear old dad.

Sean is, of course, the son of John Lennon and second wife Yoko Ono.

It’s all there; the slightly pointy features, thin bridge of the nose, willowy stride – and it doesn’t stop with physicality either. Sean has his father’s surreal sense of humour, laid-back delivery and, as he’s proven time and again with his solo endeavours, an enviable musical talent.

Obviously Lennon Jr hasn’t set the world alight in the way his old man did almost 50 years ago. But then who has? Living in the shadow of the most successful songwriting partnership of all time can’t be easy.

“I remember someone saying I was trying to look like my dad because I was wearing glasses.

“Can you believe that? I’m basically blind without them,” he says.

“But I’m used to it, those comparisons and comments. It was a huge shock to Charlotte, though,” he says, gesturing to his girlfriend next to him.

Charlotte Kemp Muhl is a 23-year-old model from Atlanta, Georgia, the youngest person to appear on the cover of prestigious fashion magazine Harper’s Bazaar, and the face of campaigns by Donna Karan, Tommy Hilfiger and Dolce & Gabbana.

She’s impossibly tall, elfin and the owner of bee-stung lips that would make Angelina Jolie jealous.

For the duration of our conversation, she remains unfussed about her breasts being on display as her loose blouse has come undone: “We’re always naked,” she says later. “It’s nothing.”