Once they were the swashbuckling pirates of the airwaves – invading our radios and defying the establishment from beyond the reaches of the law on the high seas of international waters.

Today, they are playing tunes on the internet above an estate agents office in Strood.

Fifty years on, Radio Caroline might not have entirely pulled down the sails on its rebellious past, but these days it is firmly anchored ashore and its days of flying the Jolly Rodger are long gone.

It was March 28, 1964 that Radio Caroline joined fellow buccaneers such as Radio Atlanta and Radio London in transforming the face and sound of popular radio in this country forever.

With staid old Auntie Beeb holding the radio monopoly of the UK firmly inside her apron strings, the music explosion of the early 60s needed an outlet – and the pirate radio stations anchored just outside territorial waters went there to provide it.

Groups such as the Beatles and the Rolling Stones owed much of their influence on the Swinging Sixties to airplay on pirate radio.

Pete Townshend, of The Who, is quoted as saying they would never have sold a record had it not been for Radio Caroline.

Back in 1964, Tony Blackburn - who now broadcasts for kmfm - climbed aboard the MV Caroline, then moored off the Isle of Man.

At the age of 21, it was Tony's first DJ job and the beginning of an illustrious career that landed him the honour of being the first to launch and broadcast on BBC Radio 1.

After two years on Caroline, he moved onto the American-backed Radio London.

Veteran presenter Tony said: "Radio London was always known as more professional.

"But somebody had to break the mould. The BBC had the monopoly and it took Caroline to break it. It was a terrific era. And it is great that the name Caroline is kept going."

Remarkably, the cavalier spirit lives on, half a century later.

In August, 1967, The Marine Offences Act brought an end to offshore radio with all stations closing – except Radio Caroline, the one that launched it all.

The station rode the stormy seas and carried on against all odds thanks to its string of financial backers and its listenership worldwide of tens of millions.

After a break in transmission at the end of the 60s, she returned in the 70s when the music scene had become more album-orientated.

Over the decades, she has been confronted by armed raids and international legal wrangles and was said to be the inspiration behind the 2009 film The Boat that Rocked with the late Philip Seymour Hoffman and Bill Nighy.

And, as its 50th birthday approaches, it might be prophetic that the first record to be played at midday on that Easter Sunday in 1964 was by the Rolling Stones – Not Fade Away.