OBJECTIVES: The aim of the article was to analyse the trends in oncology interventional clinical trials in the United Kingdom (UK) from 2000 to 2025, compare with major global regions, and to assess the potential impact of the New UK Clinical Trials Regulation (UK CTR) 2026 regulatory reform on the future competitiveness. DESIGN: Retrospective observational analysis of interventional oncology trials registered on ClinicalTrials.gov with comparison across the UK, European Union (EU; comprising 27 member states), the United States, and the Republic of China (China). MAIN OUTCOME MEASURES: Number of trials, phase distribution, funding source, and population-adjusted trial density across three time intervals (2000-2015, 2016-2020, 2021-2025). RESULTS: The UK experienced growth in oncology trials until 2017, followed by declines associated with Brexit and the COVID-19 pandemic, and partial recovery thereafter. While the EU and USA maintained high absolute trial numbers, both showed declining population-adjusted research intensity over time. China demonstrated the fastest growth, with substantial increases in early phase trials and trial density. CONCLUSIONS: Despite recent challenges, the UK retains strong infrastructure and expertise in oncology research; the 2026 regulatory reform may support the future attractiveness of the UK, particularly for early phase trials, although increasing global competition remains a significant issue.