Ó hAnnaidh had been charged with a terrorism offence for allegedly displaying a Hezbollah flag at a gig at the O2 Forum in Kentish Town, north London, last November.

But sitting at Woolwich crown court, the chief magistrate, Paul Goldspring, agreed with Ó hAnnaidh’s defence team, who had argued there was a legal mistake in the way the charge was brought against him.

Ó hAnnaidh told supporters outside the court on Friday: “We will not be silent.” His defence team, led by Brenda Campbell KC, argued that the attorney general, Richard Hermer, had not given permission for the case to be brought against the defendant when police informed him he was to face a terrorism charge on 21 May.