On the morning of Friday 8 August, 50 years ago, The Beatles were photographed walking across a pedestrian crossing in London.
The image of George Harrison, Paul McCartney, Ringo Starr and John Lennon striding across the road outside EMI studios in St John's Wood became the cover shot of their Abbey Road album and probably the most iconic photo of the Fab Four.
It was taken by the late Scottish photographer Iain Macmillan who stood on a ladder in the middle of the street while a policeman blocked the traffic.
The whole thing was done in roughly 10 minutes.
Glasgow-based author Ken McNab, author of And in the End: The Last Days of the Beatles, told BBC Radio's Good Morning Scotland programme that relations between the band members were strained at the time and it was just weeks before they split up entirely.
He said: "They were professionally and personally exhausted".
Mr McNab said Macmillan, who died in 2006, was very modest about the picture.
"He did not even think it was his best. It is certainly his most enduring," he said.
Macmillan was born in Carnoustie in Angus in 1938 and as a teenager he documented life in Dundee, through photographs of street life.
He moved to London and became fully immersed in the celebrity world of the late 1960s and early 70s, even living with John Lennon and Yoko Ono for a while.
He is best known for a handful of images including portraits of the Beatle and his new wife.
Macmillan also snapped hundreds of shots of musicians and models, including The Who guitarist Peter Townshend, model Twiggy and a 16-year-old soul singer Stevie Wonder.
Mr McNab said the idea for the Abbey Road photo came from Paul McCartney, who had done a sketch of what he wanted.
"Iain would arrive at the appointed hour and he had 10 minutes to get the picture," he said.
"If you can imagine him perched precariously on top of a step ladder. He had a local policeman holding up the traffic.
"They walked across the zebra crossing six times."
The one eventually chosen for the cover was number five of six. It was the only one that had their legs in a perfect 'V' formation, which Macmillan had wanted.
Mr McNab said it was one of the most iconic photos in rock history.
The zebra crossing outside the famous Abbey Road studio has become a massively popular spot for tourists to recreate the album cover.
Mr McNab said: "Iain didn't talk about it very much but one of the things he did say was that it was a very simplistic picture and it's a place where people can still go.
"It has become the most well-known Beatles shrine in the world. It must be a nightmare if you are passing in a taxi or a bus."