Sunderland's decision to move away fans at the Stadium of Light has left police with a potential security headache ahead of Sunday's derby with Newcastle United.
Ellis Short, the club's owner decided their team's fans should be housed right the way around the bottom tier of the ground last summer and put in place a new plan for the first time since the stadium opened in 1997.
Newcastle's following on Sunday will sit in the North Stand upper rather than the stand they have traditionally used at the south end of the stadium.
This presents Northumbria Police with a logistical problem in how they will keep supporters apart on their way to and from the stadium.
Tomorrow will be the 10th time Newcastle's supporters have travelled to the Stadium of Light. For the last three visits, huge steel temporary metal walls were erected to keep the neighbouring support apart.
This time, after numerous meetings, the police have tried to cope with the changes by drawing up a revised plan that is almost military-like in its detail.
Newcastle's supporters will leave in buses from St James' Park at half past 11 tomorrow morning. The convoy will have to go off road towards the north part of the stadium, and head towards the main car park outside of the Stadium of Light.
The car park the vehicles roll into will effectively be split into two. Sunderland fans will not be allowed into certain areas and, to add further barriers, the procession of double decker buses will be parked in a line running parallel with the stadium and a metal wall will be erected between the stadium and the Sunderland Aquatic Centre behind it to ensure they do not encounter Sunderland fans.
Another concern is about those who will arrive from Tyneside by train. Away fans will be directed to alight at a station which is not the nearest to the ground, St Peter's station, while, to avoid them coming face to face, Sunderland's will be directed to the Stadium of Light station on a day when all police leave in the North-east of England has been cancelled. Officers not on duty in and around the Stadium of Light will be in potential trouble spots between the two cities.
The movement of Newcastle supporters for this fixture is so complicated and the risks so high that the police plan is called Operation Jerrettspass, a reference to Irish political history. In 1798, both protestant and catholic residents in the Jerrettspass area in what is now Northern Ireland formed a branch of the Society of United Irishmen. It is an optimistic reference to harmony overcoming rivalry.
It is, in the police's eyes, a reference to the successful movement of people, for an operation so complicated that it has taken months of planning.
Operations Commander Chief Superintendent Steve Neill said: "There are a minority who are intent on causing problems and trouble will not be tolerated. Anyone who puts the safety of supporters at risk on the day will be dealt with swiftly and firmly."
Inside the stadium, Newcastle fans will watch TV screens showing their team scoring goals on the concourse behind their seats in an attempt to keep their mood good (although the assumption they will not be goals against Sunderland).
But it is their journey to and from the ground that the police are likely to be judged on.
Derby flash points
March 2012: A train carrying Sunderland fans to St James' Park is vandalised. Windows are kicked out, the roof and light fittings are damaged.
January 2011: Newcastle's goalkeeper Steve Harper is pushed over by a Sunderland fan after Asamoah Gyan's late equaliser. Rival fans fight in the stadium after the game with bottles and ripped up seats thrown.
October 2008: Shay Given is confronted by fans on the pitch after Kieran Richardson scores Sunderland's winner. Both sets of fans fight on the pitch. 29 arrests are made and an officer's wrist is broken.
April 2006: 150 Police try to clear Sunderland fans off the Monkwearmouth Bridge amid violent scenes.