Over the past eight years, traditionalist communitarian versus more liberal cosmopolitan value divides have opened and caused considerable polarization in the UK. Cleaving to Pro-Leave and Pro-Remain positions on the EU referendum question (and though posited to have waned slightly now Brexit is settled), this new identity politics has had the lasting effect of emboldening and mainstreaming radical right-wing tenets (namely, anti-migrant, anti-Islam and anti-multicultural) that were once fringe. Despite this renewed challenge and imperative from far-right extremist organizations and their concomitant attempts at inserting their viewpoints into the UK political mainstream, there is a dearth of empirical data on what works and what does not to alleviate this divide. Indeed, most evaluations on this topic tend to privilege either an ideologically agnostic approach (i.e. treating specific extremisms as functionally equivalent or co-equal), or one specifically tailored to Islamist extremism. Moreover, approaches tend to privilege individuals who have already moved a fair way down the conveyor belt of extremism, showing either commitment to a specific extremist ideology or group of organized extremist actors. This article aims to provide a useful counterpoint to these prevailing tendencies. Taking the UK as a case study, it lays out how an iterative, experimental research methodology – mixing focus groups and surveys - can be used to test counter-messaging content and, most importantly, evaluate impactful attitudinal change among far-right sympathetic audiences. It is based on over 12 months of research among far-right sympathetic users on Facebook – with an initial round of focus group testing in September 2020 followed by larger-scale online testing on the Facebook platform from February-September 2021, and involved a collaboration between CARR, ACS, M&C Saatchi, the Outsiders & Facebook, with over 36 focus group participants and a combined online experimental reach of over 1 million Facebook users.