Police are trying to trace thugs who assaulted a service station worker after Sheffield United played Hull City at Wembley.
Detectives investigating the incident at the Newport Pagnell Services on the M1 motorway said it was packed with supporters of both football teams after the FA Cup Semi-Final.
They said violence flared when an undercover store detective spotted two men stealing alcohol from the Waitrose shop at the services and challenged the pair.
He confronted the men and was struck over his head and knocked unconscious.
The shop worker fell to the ground and was kicked and punched.
Detectives want to hear from anyone at the service station who witnessed the incident.
They have issued a CCTV image of a number of men they want to trace, who they believe could hold vital information.
Investigating officer, PC Jonathan Moss, of Thames Valley Police, said it was lucky the victim was not killed in the attack.
“This was a violent attack on the victim, who is, now, thankfully recovering,” he said.
“However, the injuries sustained from being kicked in the head repeatedly could have been life changing or even resulted in a fatality.
“At the time of the incident the service station was extremely busy with fans of both Hull City and Sheffield United, and I believe that several members of the public would have witnessed this incident.
“I would encourage any witnesses or anyone who can identify the men in the images to contact me, to assist with my investigation.”
A Thames Valley Police spokesman added: “At around 9.10pm on Sunday, April 13 around 200 Hull City and Sheffield United FC fans were at the Welcome Break on the M1, northbound, between junctions 14 and 15, following a FA Cup semi-final between the two clubs at Wembley Stadium in London earlier that afternoon.
“A plain clothes store detective, who worked at the service station, witnessed two men stealing alcohol from the Waitrose shop inside the services.
“He then followed the offenders to the footpath directly next to the entrance of the services where he asked one of them to stop.
“The victim was then hit on the back of his head, lost consciousness and fell to the ground.
“While on the ground he was kicked several times, including several kicks and punches to his head.
If you have any information about this incident or recognise anyone in these images then please contact PC Moss, via the Thames Valley Police Enquiry Centre on 101.
If you don’t want to speak directly to the police you can contact Crimestoppers, anonymously, on 0800 555111.”