Which is the longest horse race run in Britain?

The longest ‘official’ horse race – or, in other words, the longest horse race run under the Rules of Racing, as defined by the British Horseracing Authority (BHA), on a pay-at-the-gate enclosed racecourse – remains the Grand National. Historically, the advertised distance of the Grand National was four-and-a-half miles. However, in 2013, for safety reasons, the start position was moved forward 90 yards or so, away from the grandstands, thereby reducing distance between the start and the first fence and, consequently, the overall race distance.

For the next few years, the advertised distance of the Grand National was four miles and about three-and-a-half-furlongs but, in 2016, was reduced again, to four miles and about two-and-a-half furlongs. The latter reduction came not because of any change to the National Course, but because of a change in the methodology used by the BHA to measure race distances on National Hunt racecourses. Nevertheless, while nowadays run over an accurately-measured 4 miles, 2 furlongs and 74 yards, the Grand National is still, far and away, the longest race in the British racing calendar.