In 1968, Graham Nash shocked the music world, as well as his family and friends, by upping sticks and moving to America.

In doing so, he left the band he had co-founded with school-friend Allan Clarke in 1962 – The Hollies.

With The Hollies, Graham had been an integral part of one of the best pop bands in music history, with hits like Stay, Carrie Anne, Jennifer Eccles and the chart-topping I’m Alive.

In the band’s three-part harmony, his was the high voice, which melded perfectly with Allan and guitarist Tony Hicks.

While on tour in America, Graham had befriended David Crosby and Stephen Stills and with them founded the eponymous Crosby Stills and Nash.

He had been experimenting musically with different sounds – especially on The Hollies album Butterfly, and found that he preferred to be a little more experimental in tonal textures.

He wrote Marrakesh Express and The Hollies attempted to record it – it was eventually shelved and Graham re-recorded it with Crosby and Stills.

“The difference was in the energy,” He tells me at his US home. “And I wanted the over-dubbed guitars to give a fuller sound.”

The result was one of CSN’s biggest hits – along with Helplessly Hoping, Suite: Judy Blue Eyes, Teach Your Children and Our House.

“The thing about Crosby, Stills and Nash was the sound we created between us with our three voices,” he explains. “I remember one night in Joni Mitchell’s living room, we started singing together and we wanted that sound. It was completely different and I loved it.”

And Graham was then able to stretch his writing talents.

“Yes, that’s right.” He says. “In England I had learned to be able to write melodies that were unforgettable, but when I moved to America, I realised that I had to write better.”

He admits that it was difficult to leave everything behind, but he is friends with Allan Clarke again.

“Yes, I rekindled my friendship with Allan and I speak to him about once a month.

Recently, Graham was honoured with a Lifetime Achievement Award at the 2019 UK Americana Awards.

“It was a really nice night,” the Blackpool-born musician says. “But you don’t get into music to win awards – it’s for the love of music.”

Graham plays the New Theatre Oxford on Sunday. And he’s really looking forward to it.

“I wouldn’t come over if I didn’t enjoy it,” he says. “There’d be no point.”

“I’ll be covering the whole of my career and I’ll be talking about the songs too. People are very interested in how songs are created, especially if they are songs that they know.”