Starmer’s resignation as the sitting Labour MP has opened Holborn and St Pancras to a by-election, with Labour’s candidate selection process only just beginning. This timing, combined with strong Green performance in the May 2026 Camden local elections across the relevant wards, has elevated Zack Polanski’s potential candidacy and kept several named contenders clustered near even money in trader pricing. Siân Berry and other left-leaning or independent figures also feature in the market, reflecting uncertainty over whether progressive votes will split or consolidate against the Labour nominee. The absence of a confirmed polling date and limited formal nominations so far leave the field fluid, with any alliance between Greens and independents or shifts in national party standing likely to move probabilities before nominations close.