On the evening of 27 August 1965, Elvis Presley and The Beatles, the music world's biggest stars, met for the first and only time.
When the Fab Four went to see the King of Rock 'n' Roll at his Beverly Hills mansion on a night off from their US tour, the initially awkward small talk gave way to an impromptu jam session.
But there are no recordings or photographs of the event.
Tony Barrow, who was The Beatles' press officer between 1962 and 1968, was also in the room. As a new exhibition about The Beatles and Elvis opens at The Beatles Story in Liverpool, he recalls that memorable night.
"When I put the idea of meeting Elvis to John, Paul, George and Ringo, they were initially put off by the fact that the press might be involved," he said.
"I remember George saying 'if this is going to be another dirty big publicity circus, let's forget it'. They did want to meet their rock 'n' roll idol, but not with a gang of reporters and photographers around to hassle them.
"The first fundamental ground rules to be set were: no press to be invited, no pictures to be taken, no recordings to be made and no leaking of our plans in advance.
"It was shortly before 10pm when we drove over. We were in a convoy of three big black limousines, led by [Elvis' manager] Colonel Parker and his people.
"The property consisted of two storeys nestled into a hillside. It was a vast, round building with a lot of windows and a spacious front garden. There was a Rolls Royce and a couple of Cadillacs lining the drive.
"Members of the famous 'Memphis Mafia' guarded the tall gates but they waved our line of limousines straight through.
"Once inside the front door, our feet seemed to sink inches into deep white shag pile carpeting.
"We arrived in the centre of the building, into this massive circular room bathed in red and blue light, and this was where the King entertained.
"This was Elvis Presley's giant playpen, complete with a colour television, a jukebox, a deep crescent-shaped couch, a couple of pool and games tables and a well-stocked bar.
"I would say, at a guess, that Presley's army of henchmen and their womenfolk must have totalled about 20 people, well outnumbering our little group.
"As the two teams faced one another, there was a weird silence and it was John who spoke first, rather awkwardly blurting out a stream of questions at Elvis, saying: 'Why do you do all these soft-centred ballads for the cinema these days? What happened to good old rock 'n' roll?'
"Elvis was fairly quiet - that was my first reaction. He smiled a lot and shook hands with everybody.
"The ice didn't really break in the early stages at all. The boys and Elvis swapped tour stories, but it hadn't got going.
"They quickly exhausted their initial bout of small talk and there was this embarrassing silence between the mega-famous five, stood there facing each other, with very little of import being said.
"Apart from anything else, I think it was just that each was in awe of the other. Elvis didn't have that much confidence, as far as I could see. He was a fairly easily embarrassed person by the look of him.
"But Elvis suddenly plugged the gap by calling for some guitars to be handed out to John, Paul and George, and a piano was hauled into view.
"Up to that point, the party really had been a bit lifeless and unexciting. But as soon as Presley and The Beatles began to play together, the atmosphere livened up.
"The boys found that they could make much better conversation with their guitars than they could with their spoken word. Music was their natural meeting point, their most intelligent means of communication.
"I can't remember all the things that they played but I do remember one of the songs was I Feel Fine. And I remember Ringo, who of course didn't have an instrument, tapping out the backbeat with his fingers on the nearest bits of wooden furniture.
"Everybody was singing. Elvis strummed a few bass guitar chords for Paul and said: 'See, I'm practising.' And Paul came back with some quip about: 'Don't worry, between us, me and Brian Epstein will make a star of you soon.'
"It would be wonderful to have either photographs or recordings. That recording would be invaluable, surely. It would be a multi-million dollar piece of tape. But it wasn't to be. It was an amazing session to listen to.
"Parker and Epstein lost interest - they were leaving the children to play. Parker put his plump arm around Brian Epstein's shoulder and led him away to a quiet corner of this playroom.
"Epstein at this point grabbed his chance to bring up the subject he'd been waiting to raise, which was his secret agenda. He hoped to persuade Parker to let him present Elvis in a series of UK concerts.
'Elvis was stoned'
"It was a hopeless project from the outset, although at the time, Parker pretended to leave the door open by saying he'd think about it.
"The party ended when Colonel Parker decided that it was time for it to end. He started dishing out presents, which mostly consisted of piles of Elvis Presley albums.
"I remember, as we went out to our limousines, John put on his Adolf Hitler accent and shouted: 'Long live ze king.' Also, John said, as we got into our limousines: 'Elvis was stoned.' George Harrison responded very quietly: 'Aren't we all?'
"They tried to make light of it and not show too much adoration for their idol, but Elvis Presley was their idol and one of the prime influences of The Beatles' music."
The Elvis And Us exhibition, which explores how The Beatles were influenced by Elvis, is at The Beatles Story for the next two years. Tony Barrow was speaking to BBC News entertainment reporter Ian Youngs.