They had gone the extra mile – and then some.
Richard Haass and Meghan O'Sullivan put brave faces on their failure to facilitate an agreement among our political parties.
Their body language showed resignation, but also regret and disappointment as they faced the gathered media for the final time.
Though undoubtedly weary, they sought to accentuate the positive and Dr Haass said people should not rush to judgment.
"I would ask you to judge the success in six months, in a year, 18 months, in two years, that would give a much more realistic definition or yardstick of what constitutes success," he said.
"What I believe we have done is laid down solid enough foundation stones," he added.
But he and Prof O'Sullivan also made clear their role in any future process will be a limited one.
In other words, they have given us their best shot.
They have been to Northern Ireland seven times in a bid to find agreement. They flew out on Christmas Eve and then flew back in on the day after Boxing Day to produce draft after draft – seven in all – which they gave the parties ample time to consider.
And they had given their services free of charge – the Executive will only have to meet their travelling, accommodation and living costs.
Although their background and experience are in academia and diplomacy, Haass and O'Sullivan both have a good grasp of real politik.
Thus, Dr Haass explained they were not here to "speak truth to power" – employing the phrase coined by Quakers in the mid-1950s calling for America to stand firm against fascism which stated, "the founders of United States risked their lives in order to speak truth to power, that of King George".
In the much less grandiose surrounds of the last few weeks, Haass and O'Sullivan said they were instead "working with power" to attempt to reach a consensus in each of the three areas.
They knew each of the parties would have to sell any agreement to their respective supporters – but also explain why they had held back from agreement.
"No one gets his or her wish-list," Dr Haass emphasised.
Even as it became apparent a fourth draft was going to be required, Haass and O'Sullivan maintained a relaxed and friendly air as they took an odd break around the environs or in the lobby of the Stormont Hotel.
And while they are said to have warned the parties about leaks to the media inside the sessions, they built up an easy and approachable relationship with an almost ever-present Press pack.
There was a telling incident on one of their first trips back, early on in the process, at the Europa Hotel, when reporters were told they would not be allowed to ask questions.
Immediately there were angry protests from the journalists, indignant and insisting they had not been summoned just to take dictation.
Press officers and officials agreed to relay the complaints and word came back that, indeed, Dr Haass would field our queries.
He did so with a confidence and aplomb that proved him well able to deal with anything put to him.
When first approached and appointed by First Minister Peter Robinson and Deputy First Minister Martin McGuinness earlier this year – and he was said to be their first choice – Dr Haass admitted stateside friends had been surprised, since they thought the problems in Northern Ireland had largely been sorted.
Prof O'Sullivan said there had been three phases to their work here – the first involving consultations, when more than 600 groups and individuals made submissions – some through the 'panel of parties' website.
In phase two, from early November, the talking got under way with each party setting out their bottom lines leading to the first draft of their proposals.
The third phase then began this month with the submission of papers and texts from the five parties, and continual refinement and 'synthesis' of the agreement document, on which there proved to be insufficient agreement despite their efforts.
Who knows what the tone of the conversation will have been as the pair flew back to the US yesterday morning, with time to ruminate on their experience in Northern Ireland.
PROFILE: Richard Haass
Richard Haass succeeded George Mitchell as the United States Special Envoy for Northern Ireland in the aftermath of the Good Friday Agreement. And he, in turn, at the end of 2003, was succeeded by Mitchell Reiss. But he was First Minister Peter Robinson and Deputy First Minister Martin McGuinness’ first choice to return here to facilitate negotiations on the divisive issues of flags, parades and the past.
Since July 2003 the 62-year-old has been president of the Council on Foreign Relations, but has also been Director of Policy Planning for the United States Department of State and was a close adviser to Secretary of State Colin Powell.
PROFILE: Meghan O'Sullivan
During her time in Iraq she was known for driving herself around Baghdad to meet the people and once managed to escape a terrorist bomb attack by scaling a hotel ledge 10 storeys high.
A graduate of Oxford University, she left work in the White House in 2007 to begin lecturing at Harvard, but was also an adviser to Republican nominee Mitt Romney. In 2008 Esquire Magazine voted the 44-year-old one of the most influential people of the century.