Today marked the beginning of a three-day counter-terrorism exercise which will continue across central and eastern Scotland and the north east of England.
The scenario, involving a vehicle attack, began at the Royal Bank of Scotland headquarters at Gogarburn.
Police Scotland, Northumbria Police, the Scottish Fire and Rescue Service, Scottish Ambulance Service, North East Ambulance Service, Northumberland and Tyne and Wear Fire and Rescue services, Transport Scotland, NHS Scotland, NHS England and the Ministry of Defence are among those taking part in the exercise, as are Scottish and UK Government ministers and officials.
City of Edinburgh, Angus and Northumberland County councils are also testing their responses to a terrorist incident in their areas.
The Home Secretary, Amber Rudd, will chair a COBR meeting as part of the exercise, involving ministers from both the UK and Scottish Governments as part of the exercise.
From this meeting, the UK Government's support to the operation can be determined and strategic discussions about how to respond to the wider threat level can take place.
Throughout the day, the Scottish Government Resilience Room has been stood up as part of the exercise to provide Scottish ministers with updates, and offer strategic direction for the Scottish Government's response.
The exercise will continue at smaller sites and individual properties across Scotland and the north east of England until 5 October.
There will be no further updates on the scenario.
No members of the general public will be involved and the exercise areas will be cordoned off and tightly controlled to minimise disruption.
It is inevitable that some noise may travel outside of the cordoned areas. This should not cause alarm and Police Scotland and Northumbria Police have taken steps to inform people in local residential and business communities what to expect.
The exercise will not affect day-to-day policing or emergency service responses, which will continue as normal throughout the exercise.
The public should continue to report any concerns they have or if they see any suspicious activity by dialling 101 or 999 in an emergency. Anonymous reports can be made to the anti-terrorist hotline on 0800 789 321.
Home Secretary, Amber Rudd said: "The events of this year have shown why it is vital that the emergency services, Government and agencies prepare and rehearse our response to potential terrorist attacks. The professionalism with which front line services dealt with the atrocities in London and Manchester is in part due to the planning and practice that goes into exercises like this.
"I will chair a meeting of COBR as part of the exercise and working with colleagues in both the UK and Scottish Governments as we test our plans to keep families and communities across the UK safe.
Scotland's Cabinet Secretary for Justice, Michael Matheson said: "Scotland has a key role to play in hosting this exercise, alongside the UK Government and other agencies. It provides an opportunity to test our response in Scotland and the readiness of our emergency services to deal with this kind of incident.
"The Scottish Government shares the commitment of our partners to taking all necessary steps to assess and strengthen our preparedness to deal effectively with terrorism.
"While fortunately such real life incidents are rare, the public can be assured that government, our blue-light services and other agencies are continuously testing and reviewing how we are best able to respond to an attack should it happen."
David Mundell, the Secretary of State for Scotland said: "The UK Government is responsible for counter-terrorism planning across Great Britain, and organises a series of exercises to help the emergency services prepare for a terrorist incident.
"This latest exercise will help the UK and Scottish Governments, and agencies including the Ministry of Defence and emergency services north and south of the border, prepare for a possible terrorist attack in Scotland.
"The current threat level for international terrorism in the UK is severe, meaning that an attack is highly likely. We know from recent incidents in London and Manchester that there are those who seek to destroy lives and communities in our country, tearing at the heart of what we hold dear.
"Our police and security service work tirelessly to detect and prevent atrocities, but we must be prepared to respond effectively to an attack. Exercises like this will ensure that our public services are as well prepared as they can possibly be, to ensure public safety and bring the perpetrators to justice swiftly."
Assistant Chief Constable Bernard Higgins from Police Scotland said: "Police Scotland and other police forces throughout Britain regularly assess and exercise their counter terrorism resources and capabilities to ensure we can respond appropriately to any incidents, which may arise.
"Exercise Border Reiver is the culmination of months of planning with partner agencies from across the UK and the scenario that will unfold over the three days is a realistic, challenging and complex set of circumstances that could arise during a terrorist incident.
"In addition to uniformed officers, a range of specialist Police Scotland resources will be in play for the exercise and this will result in some significant activity within the public domain. Please rest assured this all forms part of the live-play scenario and there is no risk to the public.
"The public should be reassured that we are constantly testing and exercising our plans along with our partners. Police Scotland is committed to ensuring that Scotland is capable of responding to the terror threat that faces the UK."
Assistant Chief Constable Darren Best of Northumbria Police, said: "This exercise has been organised to test the response of the emergency services and other partner agencies to a cross-border incident. It is in no way linked to a specific or increased threat in our region.
"We regularly carry out exercises to test contingency plans and the co-ordination of the response to a major incident to ensure we are prepared to keep our communities safe.
"We want to reassure people the exercise will not affect day to day policing and emergency service response which will continue as usual throughout the exercise."