Sergeant Pepper's Lonely Hearts Club Band, by The Beatles

Following in the footsteps of John, Paul, George and Ringo, from around the world, Beatles fans flock to London's Abbey Road, the street where the “Fab Four” turned their memorable lyrics into music a generation cannot forget.

It was at the Abbey Road studios where, perhaps, the Bealtles' most famous album was born.

Sgt. Pepper's Lonely Hearts Club Band was an immediate critical and popular sensation – described by fans, music critics and fellow musicians as innovative in every sense.

It was an adventure in concept, sound, song writing, studio technology – not to mention Sir Peter Blake's eye-popping artwork on the cover.

Released on June 1^st, 1967 the album launched the “Summer of Love” – the psychedelia, spirituality, and acid craze that swept the globe. 

At the time of its release The London Times newspaper described Sgt. Pepper as "a decisive moment in the history of Western civilization."

But behind the scenes it was the result of a staggering 129 days, or some 700 hours, the Beatles spent in the studio – recording, experimenting and mastering the album.

Richard Porter runs the Beatles in London Tour. He says the way the Sgt. Pepper concept connected songs together seamlessly created a new standard to follow, turning albums into the prevailing format instead of singles.  "For a long, long time the album was king, people used to put lots of effort into singles but then after Sgt. Pepper it was albums that became the thing to do."

For many Beatles fans, coming to Abbey road is about coming to see the place where musical nostalgia was created for a generation.

"It was a bit weird and unusual, it was different from a lot of their other music,” said one visitor.

"I remember the day i graduated from high school,” recalled another, “I went down and bought Sgt. Pepper and took it home with some friends and stayed and just listened to it all day."

"Influenced all music, all music from rock and roll. New era from Sgt Pepper for all,” said another music fan.

Forty years and 12 million copies later, Sgt Pepper is still going strong. Now it is being bought by the sons and daughters of the generation the album was originally aimed at.

The HMV music store still sells albums today recorded by The Beetles 40 years ago

Genarro Castaldo from the HMV music store says Sgt. Pepper still appeals to younger audiences. "You get a lot of TV and magazine polls that constantly put the album at number one or in the top five, and that usually serves to spark the interest of a new generation."

But these days, that new generation uses the latest technology to hear the 40-year-old music.

As comfortable with downloading Mp3s as her father was putting needle to vinyl in 1967, 11-year-old Anya from Washington DC is proof that not only has Sgt. Pepper's appeal spanned generations, it has spanned the globe too.

On its 40th birthday Sgt. Pepper came in number one in a Capital Gold radio poll in the UK. The radio network's DJ, David Jensen says the album will continue to be popular because of the mystery that surrounds it. "What were some of the songs really about?  What were they intending?  I think that has fared its popularity and a certain amount of intrigue as well."

And when the Beatles' entire back-catalogue is made digital for the first time, music retailers in the UK predict continued success of Sgt. Pepper, perhaps helping cement the album as a musical milestone for another 40 years.