Alex McKechnie, then 16, was in the crowd for that first show and went on to be a regular at the club:
"I saw The Beatles a few times in the north end of Liverpool and was working in Liverpool city centre as a messenger boy in a printing works when I heard that they were on at the Cavern in a lunchtime session.
"The Cavern was in the basement of a three or four storey warehouse. The public went down one flight of stone stairs and then there were three long arches.
"At the end of one of the long arches was a little tiny stage. That's where the Beatles performed 292 times.
"I remember it being very highly charged with excitement. The music sounded even more exciting [than the previous gigs] because The Cavern was this little squashed space so the music sounded a bit louder, a bit more exciting and a bit more vital. About 20 to 30 people were there.
"The Beatles were the complete package - they didn't just have a great singer, they had two great singers. They always did harmonies right from the very first time I saw them.
"They could probably only afford two microphones, and so when one was doing the lead singing the other two were facing each other on the mic, and it was quite charismatic, it was nice to look at. They had a camaraderie about them.
"I never heard them singing one of their own songs because they were just a straight covers band at that time, as was everybody else in Liverpool.
"The standard songs that they sang - them and the other bands in Liverpool - were [by] Chuck Berry, Little Richard, the Everly Brothers, Buddy Holly. The sound that I very clearly remember the Beatles playing in the Cavern was a Chuck Berry riff.
"As well as doing the stock standards, the Beatles were a bit different because they were better at playing complicated chords. The Beatles were a bit more adventurous.
"It wasn't just the music and the singing, it was their lack of respect for the audience. At the Cavern for those first few gigs, they were quite irreverent to the audience and other people. They were sort of the first punk band. The Beatles were a law unto themselves on the stage.
"They were still doing that when they went to America - if someone asked them a question they didn't give a serious answer, and that's how they behaved on stage in the Cavern, and that's why I think they liked it in the Cavern.
"They were the epitome of rebellion in Liverpool because they weren't trying to imitate Cliff Richard and the Shadows doing little in time steps. They would dance out of step on purpose.
"That was their purpose in life - to upset the apple cart. They were so cheeky and so entertaining all around. They were a little bit of a voice for us against authority. I think they were rebels. We were mini rebels supporting them.
"Of course when I went back to work I used to stand gazing out of the window thinking about the Beatles and the girls at the Cavern. I couldn't really concentrate on doing any work.
"Just in a few weeks they'd gained a bigger following. When word went around, the crowd grew and people kept coming back. Once you'd seen them, not many people didn't go to see them again.
"They had big long queues, right down the length of the street and even round the corner at the bottom. But at that stage I'd dumped them.
"They started talking about going to London and making records and things like that. Betrayal.
"I wasn't the only one. I think the ones who thought that they'd discovered them were a little clique and really did give up on them when the masses found them. It was only when I heard Love Me Do on the radio that I started getting interested in them again. My wife subsequently bought all the LPs but that first era of The Beatles was over for me."
Alex McKechnie was speaking to BBC News entertainment reporter Ian Youngs.
The Cavern is celebrating the anniversary with a series of tribute events on Wednesday. A documentary about the first gig will be broadcast on ITV1 at 2240 GMT on Wednesday.
It was 50 years ago today that The Beatles played their first gig at the Cavern Club in Liverpool - the venue where the band built their reputation and where Beatlemania was born.