An invasion in excess of 20,000 Rangers supporters is expected in Barcelona for tonight’s Champions League match, prompting Kenny Scott, the Rangers head of security, to speak in blunt terms last night about the potential for trouble.

The Spanish authorities have categorised the match as “high-risk” and Rangers officials are clearly nervous behind the scenes. A further complication is that, in the face of Uefa advice, Barcelona have announced that they will admit ticket-holding Rangers fans to areas of the stadium where the home supporters are gathered. Rangers “officially” have 5,000 tickets.

While Scott said he was not anticipating any trouble, his analysis of the situation last night was still quite startling in its language. “While we are not expecting trouble, there are no guarantees in these situations, and what we would say to our fans is, please behave and follow the police’s instructions,” he said.

“Let’s be realistic: we expect some of our supporters to come here and drink heavily. And that’s where the risk comes in. The risk comes when people drink heavily and then there is minor confrontation, and then it escalates into confrontation with the police.

“So we say to our fans, OK, have a drink and enjoy yourself, but try to behave responsibly. And please do what the police tell you.”

There is confusion about the ongoing sale of tickets, with Barcelona claiming it has stopped, with 92,000 already sold. It would seem an unlikely attendance figure on the night, even with so many Rangers fans arriving and clamouring to get into the game. What is obvious, though, is that no strict segregation will exist.

“It is anybody’s guess what we can anticipate in terms of overall behaviour,” Scott said. “All I can say is that we’ve had positive behaviour at our other games, though clearly we have a vast number coming out here who haven’t been at these previous matches.

“Our supporters react better to people speaking to them as opposed to guys with helmets and batons acting in a confrontational manner. That type of policing has got no place in Europe any more. The way forward is to try to facilitate the enjoyment of the fans and only present confrontation on that small percentage of fans who pose a real threat.

“In general, our supporters do not present a threat to disorder. But they have a Scottish psyche – they don’t like being bossed about.”