The atomic symbol of potassium, the maligned protagonist in Franz Kafka’s The Castle and the unspecified superior feature of a certain breakfast cereal: the letter K denotes and relates to many things. Tentatively established back in 2006, Radio K has steadily established itself as Belfast’s go-to weekly alternative club, set in the suitably underground surroundings of the basement of Belfast’s oldest bar, McHughs at Custom House Square. Casting our eye back to its foundations and the years that have since passed, we catch up with the club’s main players to trace the supremely soundtracked trajectory of a Belfast social institution.…