Inevitably the burning question of Syria, and Russia’s influence, is elbowing its way in from the fringes.
A fifth, unofficial, theme is the promotion of Northern Ireland as a model for conflict transformation and a place for G8 countries to invest.
That, more modest, objective is the one on which most progress is likely to be made.
Today, at around 3pm, Mr Cameron will greet the G8 leaders and then swiftly hand them over to Martin McGuinness and Peter Robinson who will host a reception tea for them in the Lough Erne Golf Resort’s library.
That will be an attempt to pitch the province for a G8 branded trade and investment conference here in October.
Barring a bomb or other disaster, this is something that is unlikely to go wrong. The US is backing it and other countries are likely to turn up.
Mr Cameron could say the same for the current conflict in Syria.
His last meeting before departing for the G8 last night was with Vladimir Putin, the Russian leader. Mr Putin is staunchly opposed to the proposal by the UK, France and America to arm rebel forces with the sort of heavy weaponry they need to take out Syrian government tanks and aircraft.
There is, journalists were told in Foreign office briefings on Saturday, little prospect of movement from the Russians who have, in the past, supplied many of the tanks and planes held by Bashir Assad’s Syrian regime.
Mr Cameron’s hand is weakened by a backlash from Tory MPs. They fear that any weapons supplied could fall into the hands of Islamist militants who could then use them against western forces.
There is no guarantee that his party would back him; it could even become a confidence issue.
Mr Cameron’s best hope is that Mr Putin will pressure the Assad regime to join a peace conference with the Free Syrian army.
Then the threat of arming the rebels would bring pressure on the Assad regime to settle. This is a strategy which Mr Putin can make or break if he holds his nerve, and he usually does.
The issue could well be on the agenda during talks between Putin and US president Barack Obama when they are scheduled to meet at 5pm.
The official ‘T Agenda’ of tax, trade and transparency is built on the premise that we would have an economic recovery if trade barriers could be reduced and multinational companies paid their taxes where they earned their income.
There are negotiations to free up trade between the G8 countries, especially between North America, Japan and Europe. The UK estimates that if these negotiations succeed the world’s income would be boosted by £636.68bn a year.
It is also estimated that completing the agreements would boost the EU’s GDP by £100bn a year.
The fear is that if trade is freed up it will give multinational companies even more scope to move profits around.
The Irish tax regime has re
cently been under scrutiny. It not only charges a low rate of corporation taxes on businesses, 12.5%, but is also at the centre of a number of schemes which allow companies such as Apple to practically avoid tax altogether.
These generally involve setting up Irish registered offshore companies in overseas tax havens, where they do little business, and shifting their income there. The more trade is freed up and ‘red tape’ is cut down the easier it will be to do this sort of thing on an even bigger scale.
That is where the transparency regime comes in. Mr Cameron has already asked tax havens in British dependencies to disclose the ultimate owners of companies registered with them. Third world countries suffer heavily on mineral profits.
The US often loses out through profit shifting. Yet even some American states like Delaware do not keep the sort of the records being asked for.
Closing the tax loopholes would require global agreement to work.
There is a big incentive for every individual country to line its own pockets at the expense of the others.
Mr Cameron will have done well if he can secure even outline agreement.