It had all seemed so peaceful at the start, with Rangers fans enjoying the sun before one of the most important games in their club’s history.

The day began with a carnival atmosphere. A sea of blue-clad fans sang and danced as they counted down the hours to the game. Then, at 7.30pm, 15 minutes before kick-off, as anticipation mounted, the screen in the fan zone at Piccadilly Gardens - where up to 20,000 supporters had gathered - went blank.

The fans, most of whom had been drinking all day, reacted with fury. After throwing bottles at the screen - and allegedly at the technicians trying to fix the problem - they spilled out on to the streets. Hundreds of police, including mounted officers and dog units, moved in to control the crowd but were also showered with glass bottles and cans.

By 8.30pm there was mayhem in the area surrounding Piccadilly Gardens. Fans and police clashed in pitched battles as lines of riot officers charged the mobs.

By 10pm more riot police had arrived in armoured vehicles as terrified fans and families, who only a few hours earlier had been enjoying the festival feel of the day, fled in terror. In the end, so too did some police, after being vastly outnumbered by supporters.

The question being asked yesterday after the violent scenes were shown on television was: where did it all go wrong? Was it down to a vicious minority of brutal thugs, or was it a disaster waiting to happen at a badly organised event?

Some fans arriving back in Glasgow from Manchester yesterday blamed overcrowding and overzealous policing; the police accused some Rangers fans of behaving no better than animals.

The truth, as ever, is probably somewhere inbetween. It had been obvious from early in the day that the city was not as well prepared as it should have been for the arrival of 150,000 fans.

At 9am, ticketless supporters who had travelled through the night headed straight for the three fan zones to claim a place. Within an hour of opening, Piccadilly Gardens, the nearest area to the train station, and close to the city’s hotels, restaurants and pubs, was almost full. It was an ominous start. Fans had ten hours in the baking sunshine with nothing to do but drink.

Most just wanted a good time. Hazel Macleod, 28, from Glasgow, who drove through the night to reach Manchester at 6am, was among the crowd who entered Piccadilly Gardens as soon as it opened. “We came in to pick up some programmes and couldn’t believe it was already jumping,” she said.

Ally Clark, 19, from East Kilbride, had also arrived early. “We don’t have tickets so we wanted to make sure we could see our heroes on the big screen,” he said.

Fans who had painted their faces, or donned wigs and hats, created a festival feel. Families attending the event said that they felt safe - a mood that was not to last.

By midday the party was in full swing, yet portents of the chaos to come were beginning to emerge. The amount of drink being consumed was the first and most obvious sign. Many fans were carrying cases of lager, and it was no surprise that many off-licences ran out of alcohol, with hundreds of supporters queueing outside supermarkets to snap up the remaining supplies.

Another problem was caused by the volume of people entering and leaving the fan zones simultaneously, because the mobile toilets were located outside. Glass was banned from the areas, but security staff were overwhelmed by the numbers and struggled to check every bag. All over Piccadilly Gardens, bottles of Buckfast peeped out of carrier bags.

As more supporters poured into the arena, and another busy enclosure at Albert Square, city officials realised that they had a potential public safety problem on their hands.

Shortly before 1pm a message flashed on the screens instructing fans to move to an almost empty fan zone which had opened earlier at Cathedral Gardens. There, with a capacity of 5,000 and stalls selling food, it was a more refined affair. But for the supporters who followed instructions and left Piccadilly Gardens, the subdued mood served only to highlight the mayhem across the rest of the city.

David Smith, 45, from Falkirk, said that he was disappointed by what he described as poor management of the event. “I think Manchester has been overwhelmed,” he said. “They weren’t prepared for this.”

By mid-afternoon, as the heat and the drunkenness intensified, the mood became more boisterous and edgy. The sectarian songs, which earlier had been confined to a few isolated groups, began to be sung by tens of thousands of fans, their inhibitions washed away by alcohol. In Scotland they could have been arrested for committing a religious-aggravated offence, but in England there are no such laws and by that time the supporters didn’t care. Even if the police had possessed the relevant powers it is doubtful they would have been able to exercise them.

When city officials look back on the events that led to Manchester becoming a battle zone on Wednesday night, they will find that the clues were apparent from early on.

Alcohol, passion and no small amount of machismo is a potent combination. Mix it with confusion and a lack of information and infrastructure, and disaster can quickly loom. Only hindsight will suggest how it could have been prevented.