It happened at 17:55 hours on Wednesday 11 July 2018 at the Black Sheep Brewery Tent during the Great Yorkshire Show. A member of security was injured in an unprovoked attack by three males. The incident was caught on camera by a member of the public.
The victim sustained a fractured cheek bone and cuts to his face and head.
Officers are asking members of the public to get in touch if they recognise the people in the images as they believe they will have information that will help the investigation.
If you wish to remain anonymous, you can pass information to Crimestoppers on 0800 555 111.
Please quote reference number 12180125493 when passing on information.