Just had this in by mail:
Closed to vehicles cyclists and pedestrians, but the way are not sure they have the legal power to stop horse riders!
Schedule 33A
U7003 From a point approximately 3km from its southern junction with the A591 (X: 331567 Y: 515372) extending in an overall westerly direction to a point approximately 3.1km from its southern junction with the A591 (X: 31322 Y: 515440).
The use of barriers in support of the restrictions is permitted by Section 92 of the 1984 Road Traffic Regulation Act, however horse riders will be able to pass if they so choose. The Council will ensure that signage is erected to make horse riders aware of the danger together with signage that the road is closed to vehicles (including pedal cycles) and pedestrians.