There have been several variants of U21 over the years. One in use in 2013 period was short, another in 2018 remained on the main road but the finish was near a junction. The latest variant has is based on the 2013 version and includes the left turn onto the A348. It has been measured and is the correct length.
Start at western end of tarmac strip at top of Prowse’s Lane at junction with A371 (Cross Lane) at western edge of Axbridge. After start L turn onto A38, then proceed south on A38 to turn at East Brent Rbt (5.35 miles) Return north on A38. Finish on A38 at first full drain in road surface north of the 2nd bridge north of MAW pet and farm supplies (this is Middle Rhyne not the Cheddar Yeo) about ½ mile short of the New Inn cross-roads.