It changed the face of radio and the music industry - and still holds fond memories for children of the 1960s, who delighted in a broadcast style that was revolutionary for its time.
And this weekend, listeners and DJs are making an emotional journey to the east coast to mark the 50th anniversary of the closure of pirate radio and the lasting impact it has had on the airwaves.
Frustrated by how the BBC wasn't moving with the times, unlicensed stations such as Radio Caroline and Radio London began illegally broadcasting on medium-wave frequencies from ships off the UK coast and disused sea ports.
They immediately struck a chord with listeners such as Tom Edwards, who at that time lived in Norwich and worked as a blue coat at Pontins in Pakefield, near Lowestoft.
'When I heard it, I more or less fell in love with it,' he said of listening to Radio Caroline in 1964.
'The public had never heard anything like it before. It attracted lots of attention and listeners. The BBC was very staid.'
Mr Edwards sent tapes of his Pontins tannoy shows to Radio City in the hope of landing a job on the air.
He was contacted by its manager, Reg Calvert, which led to him spending the next two years DJ-ing from the Shivering Sands towers off the Kent coast.
'I certainly realised I loved being a broadcaster,' he said, learning to ad-lib live on air and gain listeners' trust with a conversational style that was the antithesis to the BBC's formal tones.
The stations also played continuous pop music, which at that time BBC stations did not.
But moves were already underway to take the pirate stations off the air.
The government claimed they were blocking radio frequencies needed in an emergency - something hotly contested to this day by pirate radio broadcasters.
Despite the fact the stations were breaking the law David Clayton - a former editor of BBC Radio Norfolk, who listened to Radio Caroline while working on the Gorleston seafront as a teenager - said: 'As listeners we didn't care. They were playing our favourite records.'
The beginning of the end came in 1966, when merger talks between Radio City and Radio Caroline collapsed and a row broke out about payment for a transmitter delivered to Shivering Sands.
The former sea port was raided by men sent by Mr Calvert's business associate, Major Oliver Smedley - who shot and killed Mr Calvert the next evening in a scuffle at Major Smedley's home.
Mr Edwards - who was briefly senior DJ in charge moving to Radio Caroline - said the incident 'gave our government the impetus to race through the Marine Broadcasting Offences Act'.
Passed in 1967, the legislation forced many stations such as Radio City to close - although Radio Caroline continued to broadcast on and off until 1990.
Mr Edwards left the Radio Caroline ship 12 hours before the Marine Broadcasting Offences Act became law, saying: 'If I had stayed, I would've been arrested.'
But he said: 'The public outrage was enormous.
'There were 22m listeners jumping up and down. The government had to do something about it.'
Shortly afterwards the BBC launched Radio 1 and Radio 2, which also celebrate their anniversaries this year.
Many former pirate radio broadcasters like Mr Chapman went to work on those stations or new local radio stations that were being set up, bringing their broadcast style to the corporation.
'I think we realised we were doing something very different - and the public loved it,' Mr Edwards said of his time on pirate radio.
Mr Clayton added: 'It absolutely filled a vacuum.
'Pop music was everywhere at the time but you just couldn't hear it. The BBC was doing a great job and putting out some great radio but it wasn't pop music.
'The BBC was so scripted and these guys just had some fun. They really changed the way it was all done and made the BBC seem so outdated.
'That style of talking to people, being with them and being their mate was forged in the pirate days.'
Commemoration event
LV18 Lightvessel, moored in Harwich, is the host for a pirate radio tribute weekend which began on Saturday and runs until Monday, August 14.
Presenters such as Johnnie Walker, Roger Day, Tom Edwards and Norman St John taking part in the event.
Pirate BBC Essex programmes will broadcast live from the ship on Monday, August 14, from 9am to 3pm on all frequencies for the first time.
There will also be a unique link up with Radio Caroline during the afternoon.
The vessel is a star in its own right, having featured in the 2009 film The Boat That Rocked, which was based on the 1960s pirate radio movement.
Organisers are expecting around 6,000 people to visit during over the three days, with a pirate exhibition on Ha'penny Pier and a special screening of The Boat That Rocked also planned.
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