The Marine Broadcasting Offences Act, (known as the "Marine Offences Act"), became law in the United Kingdom at midnight on Monday 14 August 1967. It was introduced by Harold Wilson's Labour government in an attempt to preserve the BBC's monopoly of radio broadcasting.

The radio monopoly was that of the Post Office, which licensed the BBC exclusively to broadcast radio programmes. The BBC was in thrall to the Musicians' Union, which severely limited what it called "needle time" in order to protect jobs for live musicians. The result was that pop music was limited to a couple of programmes a week, notably "Two Way Family Favourites" at lunchtime on Sunday, the BBC's most popular programme of pop requests for members of UK forces serving overseas.

Teenagers who wanted to listen to pop music had to tune in to Radio Luxembourg, outside UK jurisdiction, broadcasting on 208 metres with somewhat patchy reception in parts of the UK. That all changed in 1964 when Irish entrepreneur, Ronan O'Rahilly, spotted an opportunity to bypass the BBC monopoly by broadcasting from outside UK territorial waters. A ship with a giant antenna set sail, and in March 1964, Radio Caroline began broadcasting non-stop pop music to an enthusiastic audience that soon swelled to millions. The station paid for itself and turned a profit by running adverts, something the BBC frowned upon as against the spirit of public service broadcasting, and had never itself done.

Radio Caroline was joined by others, and soon over a dozen broadcasting ships were dotted around the UK coastline, just beyond the 3-mile limit. They were dubbed "pirate radio" stations, and featured Radio London, Radio Scotland, Radio 270 and others. They were hugely popular, drawing audiences that far exceeded those listening to the BBC's output of programmes such as "Music While You Work" featuring live studio musicians.

The government’s heavy-handed response was the Marine Offences Act, which made it illegal to visit, supply or take adverts on ships broadcasting from international waters. On August 14th, 1967, the pirate stations went off the air one by one before midnight came. The exception was Radio Caroline, which continued to broadcast, supplying itself from the Continent, even though this was now against the law. In St Andrews as a student, I had to rig up an aerial that stretched round my room in order to tune in to it. We campaigned for free radio and published pamphlets about it, ones that gained some national prominence.

The epilogue was that we convinced the Conservatives of the case for free radio, and the party promised to introduce commercial radio when it next gained office. It won the 1970 election and legalized commercial radio broadcasting during its term in office. The BBC huffed and it puffed, but it was too late to blow the house down.