For an England fan in the west German city of Gelsenkirchen ­requiring a Euro 2024 match guide or a free Panini sticker book, Friedrich Schellhase, 30, is the go-to man. From a trestle table at the front of his small white marquee on the city’s central Heinrich König Platz, Schellhase is handing out a host of freebie pamphlets and Uefa-branded pens this weekend.

He is also watching. A social worker whose speciality is helping the hardcore “ultra” fans of the Bundesliga club Schalke, Schellhase is one of a small army of observers in the city tasked by local authorities with sounding the alarm at the first sign of trouble before England’s game against Serbia on Sunday evening.

He was looking out, he said, for “movement, someone wearing Fred Perry, you know, an attitude”.

“It was funny, there were four England fans having a drink over there last night,” said Schellhase’s ­colleague, pointing to a nearby bar, “and ten observers watching them. It was all fine, everyone was having fun.”

More than 30,000 England fans – only 20,000 of whom are believed to have tickets – are expected in Gelsenkirchen this weekend, along with a further 10,000 Serbians, for the game that is making the organisers more nervous than any other.

The tie was designated as “high risk” soon after it was drawn given the reputation of the two fan bases, with the police last week warning that up to 500 Serbian hooligans bent on violence could be on their way.

Serbia’s open training session had to be halted on Thursday when pyrotechnics were launched at the police after security guards had stopped a young fan from getting on the pitch.

Rather than stamp down on hooliganism, the Serbian state has been accused in recent years of coopting them to attack LGBT protesters and breach the Kosovo-Serbia ­border crossing.

It is considered likely there will be some from Serbia out to cause trouble, but Peter Both, Gelsenkirchen’s chief of police, suggested during a press conference on Friday that one imponderable remained: the ­modern-day England fan.

The freedom of fans to travel was heavily curtailed during the last Euros due to Covid, while the lack of alcohol and the high expense of the Qatar World Cup made that a peculiar football event.

There is now an untested generation of England fans who were teenagers at the last European tournament in 2016. “And today these fans are in their mid-20s, so they are at a stage where they might also switch to becoming part of an aggressive camp of fans, but, of course, it makes it difficult for us to predict exactly what will happen,” Both said.

That there is any question over how a cohort of England fans might react to provocation – or indeed the opportunity to cause trouble themselves – is testament to the revolution in the behaviour of England fans in the last two decades.

Once famously the carriers of the “English disease”, whose symptoms included urinating on and then trashing city centre bars, those travelling with England were awarded “fans of the tournament” at the last international football event in Germany, the 2006 World Cup.

Enjoying a beer outside Cafe Eis on Heinrich König Platz, Ashley Brown, 55, a retired fireman from north London, recalled being in Marseille in 1998, one of the many shameful ­chapters in the sorry story of English football, when the city’s port hosted three days of violence around an England tie with Tunisia.

“The England fans then are not the England fans now,” he said. “There will always be some idiots but it isn’t anything like it was.” Brown and his son, Jacob, 28, a car mechanic, go to most of England’s home games. “I’ve never seen any trouble with England,” Jacob said.

There are, however, a few warning signs to keep the German police guessing. A downward trend since 2013 in the number of arrests at domestic football games in England and Wales has been sharply reversed post-Covid, with the number now at the heights of a decade ago.

As of August 2023, there were also 1,624 football banning orders in force, which is an increase of 24% compared with the year before. Within the 2022-23 football season, 682 new banning orders were issued, an annual increase of 32%.

Then there were chaotic scenes at the final of the last Euros at Wembley, when thousands of people, many high on cocaine and without tickets, tried to storm the national stadium.

“I’m going to paraphrase Martin Luther King: ‘Happy people don’t riot’,” said Dr Mark Doidge, a reader in the school of sport, exercise and health sciences at Loughborough University. “We’re in an election cycle where the parties are not really talking about what’s positive, it’s more about just: how do we deal with the crumbling infrastructure?

“These young men are often going to be the ones who were at school when Covid was happening, those formative years. One of the positives of football is that it gives you a sense of belonging, it gives you a sense of identity, a sense of place, a sense of sociability. But then it can spill over into other things like violence.”

Professor Geoff Pearson, from Manchester University, who has advised the Home Office on hooliganism, said he believed the authorities were getting the situation under control at home and that the German police response would be key on Sunday.

He said: “It tends to be poor policing that leads to mass disorder. Even if you’ve got 100 Serbian hooligans looking to confront English fans, firstly, if they’re travelling from Serbia, they’ve got to get into Germany, and we know that there are border checks.

“Secondly, they then have got to get through Germany to Gelsenkirchen, and then they’ve got to find English fans while, at all times, avoiding the German authorities who have quite harsh powers of preventative arrest. So I think probably the Germans are best placed of anybody really to manage that, if that situation arose.”

Pearson said the ­latest generation of England fan should not alarm the German authorities and that they would likely take over the closest Irish bar or central square to “chant 10 German bombers and throw beer in the air, keep footballs in the air and engage in what might be considered quite obnoxious behaviour”.

He added: “If the German police do what they did in 2006 that won’t be a problem because they will have dialogue officers in the crowd, and they will have words with people that are stepping over the red lines, but they won’t intervene unnecessarily.

“And, of course, the police will also be keeping an eye on the Serbian groups. I would be very surprised if Serbians were able to get around the police, and if they weren’t able to manage the low-level sort of obnoxious behaviour of a lot of England fans.”