So many people have been anointed the ‘Fifth Beatle’ that the band’s number easily outstrips the actual Fab Four. Yet apart from Stuart Sutcliffe and Pete Best – the original bassist and drummers of the band, and possibly the most unfortunate men in the history of popular music – few can stake a better claim to this mythical crown than the photographer David Magnus.

Magnus first photographed the band in 1963, during a concert at Stowe School in Buckinghamshire. He was only 19 at the time, younger than his four subjects. As the Beatles went stratospheric, Magnus continued to enjoy unprecedented access to the group.

The photos presented above were taken at EMI Studio One in Abbey Road Studios over the weekend of 24-25 June 1967, as the Beatles recorded ‘All You Need Is Love’ for the first time during a live broadcast on the BBC. They include the final photograph of manager Brian Epstein – another pretender to the ‘Fifth Beatle’ throne – with the band he had discovered in the early 1960s. Epstein accidentally overdosed on barbiturates almost precisely two months later.

With the Beatles releasing Sgt Pepper’s Lonely Hearts Club Band at the start of June, these photos show the band in their creative pomp. The mop-tops have grown shaggy, the sharp suits replaced by psychedelic jackets. George Harrison waits for some tea. A young Mick Jagger looks positively doe-eyed stood next to a smoking, scowling John Lennon.

Both Magnus and the Beatles had come a long way in the four years since that concert at Stowe. Beatlemania was at its height, and the boys were now icons. Within three years they would split up forever.

The Beatles Unseen: Photographs by David Magnus runs from 16 March-14 May at Proud Chelsea. For more information, see proud.co.uk