The Marathon course is a three-lap route held entirely within the boundaries of Richmond Park, starting and finishing at Sheen Gate – the first lap will be approximately 12.2 miles, the 2nd and 3rd laps will be full Tamsin Trail laps (7.1 miles each) that will make the marathon distance of 26.2 miles or 42.1 km.
Race HQ / Start and Finish – see link below ;
https://www.royalparks.org.uk/__data/assets/pdf_file/0017/41642/Richmond-Park-Map.pdf
