Mounted police chased down a motorist after catching the driver using his mobile phone at the wheel.
Officers from Avon and Somerset Police turned the animals around and set off after the law breaker down the busy road through East Reach in Taunton, Somerset.
The force released footage as they begin a nationwide clampdown to reduce the number of people using devices while driving.
The mobile phone enforcement operation will be led by the National Police Chiefs' Council over the next three weeks.
Police colleagues from across the country are working together to target drivers who are using mobile phones or other similar devices while driving.
They reported that there have been more than 4,500 fatal or injury collisions on Avon and Somerset roads since the beginning of 2021.
In a video from the ASPolice Roads Policing Twitter account, two officers on horses can be seen chasing down and stopping a driver using his phone at the wheel.
When the driver stopped on a road in East Reach, Taunton, one of the officers told him: "You know you shouldn't be using your phone."
He replied with "No, no music. I have problem", to which the officer said: "But you're driving and you're on the phone and I can see there's a phone call ongoing."
The words "drivers face 6 points [and] £200 fine if caught using a phone" were posted to accompany the video.
A spokesman for Avon and Somerset Police said the video was taken on March 7.
They said the man had been issued with a traffic offence report and would be issued with a £200 fine.
He will also get six points on his licence - or he could choose to take the matter to court.
