England fans should be braced for more trouble in Lille later this week, according to a leading expert in football hooliganism.
England fans were attacked by gangs of Russian ultras following Saturday's 1-1 Euro 2016 draw in Marseille - the culmination of three nights of unrest in the French port.
Roy Hodgson and Wayne Rooney have appealed for calm ahead of England's second Group B game - against Wales in Lens on Thursday - but senior lecturer in criminal law Dr Geoff Pearson is concerned there could be more violent incidents, with Russia playing the day before in nearby Lille - where England fans without tickets have been advised to travel.
Dr Pearson, a senior lecturer at the University of Manchester, was in Marseille where trouble flared before and throughout the weekend and he told Sky Sports News HQ the "outdated" French police tactics exacerbated the situation, with Russian ultras, local French groups and English fans involved in violent scenes.
What were your experiences in Marseille?
"What I saw in Marseille was 52 hours of violence and disorder involving England fans, not always started by England fans. This started on Thursday night around midnight when a group of what appeared to be Marseille ultras approached a bar with around 250 England fans.
"There was one bottle a side thrown, I think, and a chair was thrown and the police responded to that by firing tear gas into the crowd and escalating that small incident of disorder. A similar pattern happened on the Friday, this time around 6pm - a big group of England fans, been drinking all day, but there had been no trouble whatsoever.
"There had been no missiles thrown and then suddenly a group of the CRS, who are the riot police in France, paraded in front of the England fans with shields in a sort of Roman legion, tortoise formation and there were about half a dozen bottles thrown at them and again tear gas was the response and this escalated the disorder throughout the rest of the day.
"Again, similar on Saturday, this happened at around 3pm. This time it was local ultra groups, we believe, that threw the first bottles. Tear gas, an increasing number of English becoming involved, and then into the midst of this come around 150 Russian ultras with the intent of attacking England fans."
What are the dynamics here? Local fans, Russian fans, and English fans but not necessarily the English starting problems off?
"If there were England fans there with the intention of causing violence, they were few and far between and they have been there for the last 15 or 20 years. The make-up of the England fans was the same as it had been at the World Cup in 2006, at the Euros in 2004 where around the matches, these events passed off completely peacefully, or relatively peacefully.
"So the question has to be: why has it happened in Marseille when it didn't happen at these other tournaments and these other big match events? Why don't we have these big crowd riots in England, even though we have people that attend matches with the intention of engaging in violence? So why is it that it suddenly happened now? There has to be something specific about that set of circumstances or about that policing operation which has led to this."
So, do you have any theories about why this is happening?
"The strategies the French police are using are simply outdated. They have been discarded by a lot of Europe already; they have been discarded in the UK, in Sweden, Denmark, Germany, the Netherlands, and Portugal.
"All these countries and more have moved on and recognised the value and importance of actually being able to communicate with fans, to have officers that are active within those fan groups, to talk to fans, to try and understand the make-up of that crowd, to try set down tolerance limits.
"You should have police officers in a crowd so that when two people throw bottles, they can be arrested and you can call in officers to make an arrest who don't need riot gear because you can say back to those officers 'this isn't a violent crowd, this is a crowd with just two people throwing bottles'.
"And if you make an arrest, the crowd will understand that and it will also show that you are setting tolerance limits for the rest of them. The French haven't been doing that, they've only been intervening after incidents occur, then they have been intervening indiscriminately and in overwhelming force."
So the use of riot gear and this show of force exacerbates problems?
"I think it is counter-productive - wearing riot gear when there isn't a riot taking place can sometimes lead to disorder escalating. The other concern with the French police is not just the strategy, which is outdated, but that operationally they appeared incapable of dealing with a fast-moving, organised group of ultras - around 150 of them, it was difficult to tell because they split into different groups - of Marseille ultras who were there with the specific intent of attacking England fans, not necessarily hooligans. They were there to attack England fans.
"And you would have thought that the French police would have at least been able to deal with those, even if they got the strategy of crowd management wrong, but they were completely out-thought; they were completely out-manoeuvred.
"It was actually only small groups of undercover officers with CS grenades who were able to deal with that group in the end, so the normal riot police not only couldn't manage the crowd, but they couldn't manage the hooligan firm."
What did you make of the strategy within the ground? It appeared as though Russian fans were able to move quickly towards England fans and there appeared to be no French police around?
"The stadium will be dealt with by UEFA security rather than the police but, bearing in mind what had happened, there wasn't a sufficient segregation line to keep the Russian fans in check really, bearing in mind there were ultras among them looking to attack English fans.
"Shortly before the end of the match, there was a large explosion from the Russian end which was probably a signal to those ultras to, basically, launch an attack.
"It was a neutral section so there were locals, there were Russians, there were English and a lot of families in there. This wasn't the England end that was attacked. A lot of the people I've spoken to in there talked about a small number of ultras with their faces covered, maybe 20 or 30 and then behind them a larger group of Russians just wearing normal shirts.
"I estimated from the other side of the ground around 100 essentially just walked through the segregation line and then some of those then attacked England fans and gave them quite severe beatings."
Are the Russian ultras keen to usurp the idea of English hooligans?
"Yes, I think so. England fans still have a reputation and you still see popular media and films about hooliganism, there is still this idea that the English are world class in hooliganism when in fact there are very few people involved in organised football violence in this country, the police have a good control over it.
"So, unfortunately this reputation is problematic for ordinary England fans both in terms of how they are policed and in terms of local groups, because the Marseille ultras were also attacking England fans - although not to the same extent - how these ultra groups also treat England fans.
"Also, on Sunday night there were incidents with German and Ukrainian supporters in Lille and there is talk, there is speculation about whether some of the Eastern European hooligan groups are attempting to establish or improve their own reputations at this tournament, maybe by attacking those groups where domestic football has a reputation for having some hooligan element but actually where the people at the tournament are just there to watch the football and have a good time.
England fans without tickets for the Wales game on Thursday are being told to go to fan parks in Lille where Russia will have just played the day before. Are you concerned there will potentially be more trouble?
"There will almost certainly be violent incidents in Lille. If that Russian ultra group are there, then we can assume that Russian ultra group will be looking to attack fans and it may well be that they are looking to attack Welsh fans.
"They have never attacked Welsh fans before - of course, there is a reputation in domestic Welsh football around Cardiff City. So that may well be a target for them.
"Also, we have to realise that there are a lot of English who were in Marseille who are very angry, who don't consider that the police have a control of the situation and will be wanting to take matters into their own hands and there will be the concern, that I think will be expressed in the press in the coming days, that there will be groups from England looking to travel out, essentially for revenge.
"So, I think there will be incidents, whether those incidents are just sporadic violence or whether that escalates into the sort of widespread disorder we saw in Marseille really, I'm afraid, is up to the French police."
Will there be a change in French police tactics to try and prevent more trouble on Thursday?
"I think it is possible that they will be able to change their tactics and they need to be able to change their tactics to be able to identify and differentiate these groups and to try and protect law-abiding fans.
"What I don't think they are going to be able to do is change their overall strategy which, in terms of managing crowds, has been in place since the late 60s."
Can British police help any further?
"The British can only do what the French allow them to do on their territory. I would like to see the British police more involved in a liaison capacity between the groups of English and between the French police but unfortunately that only works if the French police are willing to listen to them.
"Otherwise you just have a situation where the English officers are putting themselves in a situation where they could find themselves attacked by these local groups and by the French police, so that will only work with the French agreeing to it."