US President Barack Obama arrived in Belfast today amid the biggest security operation ever mounted in Northern Ireland, writes Lesley-Anne McKeown
Air Force One touched down at Aldergrove International Airport, 20 miles north of the city, where the President emerged from the plane with his wife, Michelle, and two daughters, Malia, 14, and Sasha, 11.
He was flown to Belfast City Airport by helicopter and then travelled to the Waterfront Hall conference centre where he spoke to an invited audience of 2,000 mostly young people and urged political leaders to develop the peace process.
On arrival at the Waterfront, Mr Obama was greeted by Northern Ireland's First and Deputy First Ministers Peter Robinson and Martin McGuinness.
Roads into and out of Belfast were closed to facilitate the president's visit.
Hundreds of police 4x4s lined the streets, while the Police Service of Northern Ireland helicopter patrolled the skies over the city.
Thousands of extra police officers were deployed to the province ahead of the G8 summit.
Even though Mr Obama visitied the Republic two years ago, this is his first trip to Northern Ireland.
Later he will travel to the luxury Lough Erne golf resort in Enniskillen, Co Fermanagh, where the leaders of the world's eight wealthiest countries will converge for the two-day G8 economic conference.
Former US president Bill Clinton became the first serving US leader to visit Northern Ireland in 1995 and was a regular visitor during the peace negotiations.
George Bush also visited Northern Ireland in 2008.
Despite the international focus on Syria, Mr Cameron made clear that his key priorities for the two-day summit are economic issues, including a planned EU/US free trade deal and measures to crack down on tax havens.
The Prime Minister has put the "three Ts" of trade, tax and transparency at the top of the agenda while the UK holds the year-long presidency of the G8.
Later today, Mr Obama and EU leaders are expected to launch negotiations on what has been dubbed an "economic Nato".
When talks conclude in 18-24 months' time, Mr Cameron believes the EU/US trade pact could be worth £10 billion to the UK economy - or £380 for every British household.
He is also hoping to forge agreement on greater sharing of tax information in order to prevent companies and individuals avoiding paying their fair share by hiding cash in offshore bolt-holes.
At the weekend the tax transparency drive was boosted by the agreement of 10 British overseas territories and crown dependencies to sign up to new OECD standards.
Mr Cameron said: "I think we have made huge progress already, even before leaders have arrived here in Northern Ireland.
"I know the scepticism there is around the country about leaders meeting, a lot of words, will things happen?
"I want to be absolutely clear that my agenda here is about helping hard-working families right here in the United Kingdom.
"We've already actually gathered billions of pounds of extra tax revenue because of this agenda, which means that I can keep taxes down on hard-working families across the United Kingdom.
"We are going to achieve more on that. If we sign trade deals and start trade negotiations here at this meeting in Northern Ireland, that will cut prices and mean a wider range of goods in shops here in the United Kingdom and jobs here in the United Kingdom.
"So my focus is very clear - getting agreements, signing deals, making progress on issues that will help hard-working families right here in the United Kingdom. For me, that's what the agenda of this G8 is all about."