OBJECTIVES: If randomised controlled trials can be successfully emulated using real-world data (RWD), confidence in the validity of RWD for estimating treatment effects for questions that have not been assessed in trials increases. We used routinely collected administrative and clinical national linked datasets from England to emulate the PR07 trial for high-risk prostate cancer patients, which compared the effects of radiotherapy added to hormone therapy (RT+HT) within 8 weeks of randomisation (the 'grace period') and hormone therapy only (HT) on all-cause mortality. We highlight methodological choices required and challenges encountered in emulating this trial. STUDY DESIGN AND SETTING: Patients diagnosed with prostate cancer from 2014 to 2020 were identified from the routine national linked datasets. Diagnosis was taken as the time zero. As few patients initiated radiotherapy within 8 weeks of diagnosis, we considered target trials with grace periods of 4-6 months. Estimands of interest were hazard ratios (HRs) and survival probabilities over 7 years. The cloning-censoring-and-weighting (CCW) approach was used to control for measured confounding and to allow for the grace period. We also used an extension (the 'landmark-CCW' approach), in which we consider several time-origins post-diagnosis, enabling us to use a grace period of 8 weeks as in PR07. RESULTS: A total of 2,690 patients were eligible for inclusion in the emulated trial. The CCW analysis using a grace period of 6 months gave an estimated HR of 0.48 (95%CI: 0.34-0.60) and 7-year survival estimates of 80.7% (95%CI: 74.3-87.0) for the RT+HT strategy and 65.6% (95%CI: 62.8, 68.1) for HT only strategy, and corresponding risk difference of 15.1% (95%CI: 11.5-18.9). The corresponding HR from the landmark-CCW approach was 0.58 (95%CI: 0.51-0.65) and with survival estimates of 80.7% (95%CI: 77.7-83.8) for RT+HT strategy and 69.8% (95%CI: 68.2-71.4) for the HT only strategy, and a risk difference of 10.9% (95%CI: 6.3-15.9). CONCLUSIONS: Our findings from the emulated trial using RWD are broadly consistent with those from PR07, with RT+HT estimated to result in better survival compared to HT only. However, the findings were not replicated exactly, with PR07 reporting a HR of 0.77 (95%CI: 0.61-0.98) over 7 years of follow-up. Differences may be in part due to challenges in defining time zero and allowing for a treatment grace period of the same duration as in PR07. Our study considered ways in which these challenges can be addressed, and our findings affirm the utility of RWD for estimating treatment effects.