Overtaking horses

If you are overtaking a horse, please start talking to it from at least 50m behind. Horses won’t know you are there and can ‘spook’, endangering the rider and you. Do not use your bell.

Reference from the Highway Code:
Rule 215
Horse riders and horse-drawn vehicles. Be particularly careful of horse riders and horse-drawn vehicles especially when approaching, overtaking, passing or moving away. Always pass wide and slowly. When you see a horse on a road, you should slow down to a maximum of 10 mph. Be patient, do not sound your horn [or rev your engine. When safe to do so, pass wide and slow, allowing at least 2 metres of space.