Large away supports in games between Rangers and Celtic have been described as unsafe by the police officer in charge of investigating Sunday's Ibrox trouble.
On-field clashes after Celtic’s Scottish Cup triumph appear to have ended any hopes of traditional allocations returning to the Glasgow derby fixture on a regular basis for the foreseeable future.
Celtic had about 7,500 fans inside Ibrox for the first time since 2018 and dozens spilled on to the pitch to celebrate their shoot-out triumph.
More than 100 Rangers fans also invaded the pitch and charged towards the Broomloan Stand.
Several police officers, stewards and members of the public were injured and nine arrests had been made inside 24 hours, with "significantly" more expected.
Recent away allocations have veered from about 750 to a complete absence to around 2,500, but Scottish Cup rules state away clubs can claim up to 20% of tickets and a deal was reached following input from the Scottish Football Association.
Chief Superintendent Emma Croft believes the allocation had an impact on the trouble.
When asked for her opinion on why hostilities spilled over, she said: "I think euphoria from the type of win and the last-minute nature of the win.
"There’s the ongoing rivalry and pent-up aggression between the two sides, absolutely. Back-to-back Old Firms probably played its part.
"And for me, also, such a large away fan base within Ibrox, which was news to many people and a new experience for many people, given the time, I think played its part, absolutely.
"That’s where I would welcome conversations – and realistic conversations at that – as to how the footballing experience can be matched with the safety experience.
"I would like to think we have an input, considering the big issue is the safety of all and policing has a big part to play in that.
"I don’t think it’s right that I say that it’s a complete ban, but what I would say is that set-up is not sustainable and not safe."
Police are investigating incidents before and after the game and inside and outside Ibrox.
A number of Celtic fans without tickets broke into the stadium and graffiti in the Broomloan Stand included references to the 1971 Ibrox disaster, when 66 Rangers fans died in a crush as they left an Old Firm game.
A lit flare was thrown by a charging Rangers fan before being exchanged back and forth, and police said a 10-year-old child had been struck by a coin.
A 47-year-old man has been charged with assault after a member of Celtic’s staff and a player were caught up in the post-match chaos.
Footage also showed a fan aim a kick at Celtic defender Julian Araujo before another ran up and pushed the Mexico international.
A review of the police operation has been launched but Chief Supt Croft feels enough officers were deployed and that they reacted "as quickly and appropriately as we possibly could".
She believes the key to avoiding similar scenes is the clubs engaging with their "ultra" groups and setting "clearer expectations".
"I would implore the clubs and the footballing authorities to really invest in that engagement with those groups, to allow them to be ultra supporters but to keep within the confines of the requirements of the club and, importantly for us, to not breach the threshold of criminality," she added.
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