A fox hunter and an anti-hunting activist have been filmed in a violent clash that saw the huntswoman repeatedly beat the protester with her riding crop.
The protester was part of a group trying to sabotage a fox hunt in the English county of Sussex on Sunday.
During the altercation, the huntswoman can be heard shouting "get off my horse" while repeatedly whipping the masked protester who had grabbed the reins of her horse.
The man reportedly received a bruise and a bump to the head, but did not require medical treatment.
During the altercation, the person shooting the video shouted, "You can't ride people down" after the rider charged her horse towards protesters in a bid to move them off the grass and back onto the road.
The protesters are members of the Brighton Hunt Saboteurs, an anti-hunting activist group that takes "direct action to stop bloodsports" and touts itself as being one of the oldest hunt saboteur groups in England.
The group posted the video of the altercation on their Facebook page, saying one rider had "lost the plot".
"Yesterday we took a trip over to the Pevensey Marshes with South Coast Hunt Sabs to sabotage the East Sussex and Romney Marsh Hunt," the post said.
"This is a hunt we haven't seen much of recently and they didn't seem too happy to see us!
"Clearly unable to reconcile with the fact that most people find her 'hobby' abhorrent, one rider also lost the plot and started riding sabs down and attacking us with her whip.
"Needless to say, we stood our ground and will no doubt be seeing the ESRM again very soon."
The video has been widely shared online, racking up more than 800,000 views.
Many commenters on social media said that while they did not agree with fox hunting, by grabbing the horse's reins the man had put both he and the rider in danger.
Sussex Police said a third party report of the assault was made, but are appealing for more witnesses to come forward with information.
"The informant was not a witness to the incident," a spokesperson said, "but police have now identified the alleged victim and an investigation is under way".