Societal crises, such as COVID-19, produce societal instability and create a fertile ground for radicalization. Extremists exploit such crises by distributing disinformation to amplify uncertainty and distrust. Based on these developments, this study presents a longitudinal analysis across three different non-violent extremist ideologies in the UK (Islamist, far right and eco-radicals). As part of the study, public social media channels Twitter/X, Facebook, and Telegram) of Britain First, 5 Pillars, and Earth First! were analyzed using a computational language classifier of over 36,000 posts between 2016 and 2021. The increasing prevalence of conspiracy narratives, as well as violent, hateful, and threatening language among the corpus indicates that radicalization dynamics were present and heightened, pre-, during, and post-Pandemic.