He swam in the lough. He poured praise on his G8 partners.

And at a closing blustery press conference by the side of the lake, he sold Northern Ireland as if it were one of the seven tourist wonders of the world. If summit hosts can be marked for effort, Cameron deserves an A*.

Though tax campaigners accused the final agreement of lacking new, hard detail, Cameron may even have achieved a legacy, persuading his fellow G8 members to sign the Lough Erne declaration, a commitment to end corporate tax evasion and clear up tax havens. In years to come, the currently wordy declaration could prove to be a point of change. There is enough detail in the communique, say supporters, to keep the agenda going for years.

Sir Mervyn King, the outgoing Bank of England governor, recently referred to "the audacity of pessimism" in reference to world summits – the backs of world leaders really have to be against the wall before they agree to do anything serious at events such as the G8, as they indeed did in 2007 during the banking crash.

Clearly, the most difficult issue at the Lough Erne summit, the crisis in Syria, is not yet deemed so bad that either Russia or the west feel sufficiently threatened to change previous positions. It is true that Cameron was not left with a complete impasse after two days trying to strong arm Russian president Vladimir Putin to abandon his support for President Bashar al-Assad. Cameron himself pointed out there had been predictions there would be no deal on Syria, or a communique signed by the G7 and not Russia, or else an agreement so weak as to be meaningless.

British officials were claiming manfully that the wording did have meaning, even though it contained no date for a peace conference, save for "as soon as possible", or any requirement that Assad stand aside to let the peace conference go ahead. Cameron's aides said the wording entangled the Russians deeper in a commitment to a transitional government than ever before, including "a governing body operating under a top leadership that inspires public confidence". They also pointed to acceptance of an independent investigation into Assad's alleged use of chemical weapons.

Cameron said: "The task now is to get on with the process of naming people from the regime, from the opposition, who can sit down and talk about a transitional authority that will take power in Syria."

Cameron also believes the planned peace talks can lure Assad's acolytes to break with their leader by vowing that if he goes, the existing military and security services will be preserved, saying the aim was "to learn the lessons of Iraq". Cameron almost made a direct appeal for insurrection by Assad's acolytes. He said "the aim was to learn the lessons of Iraq by ensuring the key institutions of the state are maintained through the transition and there is no vacuum. To those who have been loyal to Assad but who know he has to go and who want stability in their country they should take note of this point".

But judging by the reaction of Putin – his refusal to accept a capitulation by Assad, his assertion of his moral and legal right to continue to supply weapons to Assad, and his insistence that both sides in any peace talks should be able to pick their delegations – there is little reason for Assad's allies to believe the regime, or Russian support for the regime, is crumbling.

Indeed, after the summit Barack Obama focused on the need to strengthen the Syrian rebels with arms.

Cameron had promised a clarifying moment on Syria; it cannot be honestly said he secured one. It is not a breakthrough and as the French delegation said privately, such a breakthrough was never realistic. Neither Russia nor the west are able to bring their respective clients to the negotiating table. The true progress has been in the greater understanding of each other's positions.

On tax, however, one British official said the communique had "more substance on tax and development than any communique for 20 years". Cameron accepted that many will simply see it as words on a page and that there are many "shoulds" and "shalls", as opposed to commitments in the communique. But there is now a process under way on automatic exchange of tax information, on company country by country reporting, on the introduction of beneficial ownership registers in France, Italy, the UK and the US, as well as helping developing countries to build their tax base.

Among information to be shared will be who ultimately benefits from the shell companies, special purpose vehicles and trust arrangements often employed by tax evaders and money launderers.