The victory in the constituency of Runcorn and Helsby comes in conjunction with local elections seen as a gauge of opinion ten months following the social democratic Labour Party's landslide win in the parliamentary election.
Reform UK is led by discontent politician Nigel Farage, who previously led the Brexit party UKIP. When that party's goal of leaving the EU was achieved, Farage signaled that he would leave politics – but quickly regretted it, and instead talks about seizing power in the United Kingdom.
Following Labour's victory, no national election is anticipated in the country for several years. However, analysts are already describing a new political landscape.
Reform poses a significant threat to both the Conservative Party and Labour, says John Curtice, political scientist at the University of Strathclyde, to BBC.
