UK Prime Minister Keir Starmer warned Friday that authorities must “stay on high alert” for more far-right riots, as a court issued the first jail sentence for online incitement during the recent disorder. Starmer’s comments followed consecutive nights of relative quiet across England, after a week of near daily unrest in more than a dozen places after a deadly knife attack that killed three children. Disturbances have continued unabated in Northern Ireland, however, where police have blamed pro-UK loyalist paramilitaries for fuelling nightly violence in Belfast. Starmer was speaking during a …