UK police have said that Russian hooligans attacked England football fans with such ferocity in Marseilles during the Euro 2016 finals, that officers sent over to the country feared that five fans would die as a result of the violence.
Specialist officers sent to France to monitor fans said the Russians used military tactics and levels of violence not seen in England since the 1980s. Now, UK authorities are seeking assurances from Russia that fans will be protected during the 2018 World Cup Finals.
National Lead for football policing, Assistant Chief Constable Mark Roberts, said he was confident that Russia would be able to cope.
"We will not give advice to the fans that I am not happy to stand behind, so if we identify risks we will tell the supporters so they can make informed decisions," said ACC Roberts. "If we have a high degree of confidence that they can travel without issue, that will be the message."
The so-called "Battle of Marseilles" took place before and during England's match against Russia in the French city on 10 June (2016). The game had already been ear-marked as a potential flash-point due to the reputation of both sets of fans and England's history of trouble-making in Marseilles in other tournaments.
"I couldn't believe what I was seeing," Chief Superintendent Steve Neill, of Northumbria Police, told Sky News.
"The severity and barbarity of it was quite shocking. There was CS smoke drifting everywhere, tables and chairs lying around, people with blood pouring out of their heads. It was like nothing we had seen before."
Two England fans suffered "life-changing" injuries as a result of the sustained attack, but CS Neill said it could have been even worse. "I stood in Marseille as the senior officer, believing we were going to get five fatalities that night, we might have five murders on our hands."