Northern Ireland Secretary Theresa Villiers has defended the astronomical costs of security for the G8 conference in Co Fermanagh.
With just two arrests - one in Belfast and the second in Enniskillen, the venue for the summit - she declared: "It is money well spent."
It has cost at least £50 million but the final bill is expected to be considerably higher by the time the global leaders leave Lough Erne late on Tuesday afternoon.
Security chiefs said they had not anticipated any significant public disorder but privately are worried by the threat posed by dissident republicans opposed to the peace process who, they fear, might try and launch some sort of terrorist attack.
Ammunition and explosives were seized in a series of raids last week, and the thousands of police on duty will remain on a high state of alert. But the Northern Ireland Secretary was clearly relieved that the event, so far, had passed off without any major incidents.
She said: "All the money spent on security has been money well spent. The terrorist threat continues to be severe. We can all imagine dissident republicans would loved to have staged an attack when the world's media is in Northern Ireland. The fact they have been unable to do that is a tribute to work done by the PSNI to ensure a safe and secure summit.
"If that kind of preparation had not been done and a terrorist attack taken place, the impact would have been catastrophic. You have to plan for the worst. Without that excellent preparation we probably would have been seeing more public-order issues that we have so far.
"God forbid maybe we would see some problems with the DR (dissident republican) threat. It is not just a coincidence we have had a peaceful summit so far. It is in a large part because of the hard work done by the PSNI and its partners for things to have gone so well."
Details of the total security bill would, she said, be published after the summit.
Ms Villiers added: "I am absolutely convinced this summit will generate very significant benefits for Northern Ireland.....It is tremendous to show the world what a beautiful place Northern Ireland is. The backdrop at Lough Erne is absolutely stunning."