"I started a joke" is a line from an old Bee Gees song that the person telling it could not understand was a joke being played out on the teller of the story. Now read the word anorak and then the words Radio Caroline listener - to see that the joke was, and is on you!
You, as the song implies, started the Establishment laughing.
Princess Margaret and her 'Set', were the epitome of English snobbery dressed-up in refinery paid for by the hoi polloi - who existed to be exploited for the benefit of the British Establishment. In her case, it was that splinter Establishment which she and the likes of Jocelyn Stevens used to attack the main Establishment, while supposedly attacking it.
Whatever this counter-version was, it wasn't something that was supposed to attract the hoi polloi. It was in fact an internal fight within a select group of people, and their own version existed for the benefit of the titled few. Therefore, for this group to get hold of a very young Irishman and promote him as their symbol of a 'fight for freedom', was a very sick joke indeed. But a joke it was, and it was played on the British People, the hoi polloi.
Not only that, but this bunch of snobs dusted off an ambiguous tie-in to this young man's family past, as a story to be told in print about a man who was shot by British troops during his participation in a failed uprising against the British Crown. They picked a symbol that represented a slap in the face to the British Establishment, and in a Monty Python, Fawlty Towers, Yes Minister sort of way, it was probably the cause of much mirth over drinks at many an Establishment club. It was an 'insiders' joke played on everyone who has bought into it.