ANYONE who has followed a team to enough away games over the years develops what amounts to a sixth sense.

You cannot see or hear an "edge" or "an atmosphere" in a city, but if you have been around the block enough times you can certainly feel one. There are times when there is a vibe that things could kick off in a place. Some of the eye-witness accounts from Celtic supporters alluded to exactly that feeling of malevolence in parts of Amsterdam city centre last Wednesday, especially as darkness fell.

The attack on The Old Sailor pub by a gang of masked Ajax hooligans on the Tuesday evening is the sort of incident - a surprise attack by a home mob - which has a profound impact on the rest of a trip. It was clear immediately that, after a bit of a rampage in Glasgow, the Ajax hooligans felt that they had some unfinished business. Celtic supporters were correctly warned to be "vigilant" by the club but that meant the prospect, or the fear, of trouble was never far from most fans' minds. Knowing that a mob of masked thugs might turn up to smash windows and crack heads at any time is a deeply unpleasant thought in the hours before a game. A highly visible police force, some in riot gear, and plain-clothed "arrest squads" indistinguishable from local hooligans, is not conducive to a peaceful day either.

The statement Celtic issued later made much of the many complaints the club had received from innocent and aggrieved supporters citing the high level of unprovoked assaults or attention they had suffered or witnessed from the police, especially when tensions seemed to rise after a Celtic flag was stolen by Ajax supporters. It must be assumed that those contacting the club to freely proffer their accounts responded to any provocation maturely and sensibly, either by trying to defuse whatever situation they were in or else trying to get as far from the flashpoints as quickly they could.

Celtic have two things to do: help and support any of their fans who were victimised, but also establish who among their support reacted with aggression, violence and loutishness of their own. It is clear from the footage posted on social media that some did. "We would stress that there is no excuse for any form of violent conduct," read that Celtic statement. That is an unequivocal position from the club. Does provocation or "heavy-handed" policing excuse fighting, chasing and attacking a handful of guys beside a tram, throwing bottles or standing across a street challenging a line of police? It does not. A plain-clothed policeman repeatedly kneeing a fan is unforgivable, and so is beating and throwing bottles at him in return.

Celtic have had little run-ins with Uefa over crowd issues in the last couple of years but those were for a banner, chanting and fireworks. Not for violence. The club does not have a hooligan issue, there is no mob of their fans looking for trouble when the club travels around Scotland or Europe. Considering the numbers who journey with them they are impressively trouble-free. There is no reason to believe there will be any problem when they complete their Group H campaign in Barcelona.

But not every city and every police force takes kindly to more than 10,000 fans descending on it for a day or two of noisy outdoor drinking. Some citizens will always bristle at an occupation of that scale. Seville happily accommodated 80,000 and the absence of trouble spoke volumes for the Celtic support. But no two trips are entirely the same, and when Amsterdam's hooligans and police began to throw their weight around, some Celtic fans went beyond legitimate self-defence.

Only British clubs - and arguably only Celtic and Rangers - have supports which think nothing of travelling to away European group games in the sort of vast numbers which descended on Amsterdam. Who else would take 12,000 to such a game, with only 3000 of them holding tickets? It is risible to argue that every single one of them, after a long day of heavy drinking for many, and whatever the circumstances, will always behave impeccably.

Last December, Peter Lawwell, the Celtic chief executive, apologised to Dundee after crowd trouble at Dens Park, blaming a small minority and saying that other supporters had complained about that troublesome element. "It is time for all our true supporters who care about Celtic to unite with the club and find a solution to this problem," he said. Dundee's operations manager spoke of drunkenness and likened the episode to a throwback to the 1970s.

The drinking culture is endemic among travelling British fans. In the footage last week, one constant was people virtually wading through a sea bed of empty bottles, cans and beer boxes. For years there has not been footage of a stand-off between police and any set of British fans in a city centre without the detritus of heavy boozing all around. Usually heavy drinking does not equate to trouble, but it is a guaranteed part of the mix when there is any.

There is nothing Celtic can do about that. Nor can they have enough input when 9000 fly to a foreign city without tickets. But when a club does not have control over such numbers, especially in a city with a rowdy reputation, an established hooligan problem and a twitchy police force, it becomes deeply vulnerable. And real damage can be done to its reputation.