The judge, Merfyn Hughes QC, said that although John Larsen's actions in causing a series of explosions in Denbigh did not constitute terrorism in the usual sense, it was "a sustained campaign of quite deliberate terror."
More top news
Rain clipping the far north through the evening but elsewhere staying dry with some sunny spells.
Public Health Wales figures show 25 more cases of the virus have also been confirmed.
Photos taken on Saturday morning show Roald Dahl Plass strewn with empty beer bottles and discarded canisters of laughing gas.