The fact that EU leaders had already pointed to problems in the Chequers proposal long before this summit; the fact that they praised other parts of the prime minister's plan, such as her thoughts on security; the fact that numerous European prime ministers said here in Salzburg that there had more hope now that there could be a successful Brexit deal, thanks in part to the prime minister's Chequers plan - all that has now been eclipsed.
EU Council President Donald Tusk and French President Emmanuel Macron tore into May's plan for economic ties with the EU after Brexit, saying it simply "will not work" and was "not acceptable".
The prime minister also said she would present a counter-proposal to resolve the impasse over the Irish backstop, an EU proposal stipulating that if a free trade agreement can not be signed after Brexit then Northern Ireland would remain in the customs union, creating a trade border down the Irish Sea.
"But of course, language, detail, how you actually achieve those things I think any reasonable person who wants to get an agreement has to be willing to compromise on those things", he said, adding that a deal was in everyone's interest.
"The UK will leave on March 29 next year", she said over dinner, adding: "The onus is now on all of us to get this deal done".
Mrs May promised new proposals to reassure Dublin that it would not end up with a "hard border" with the British province of Northern Ireland but warned that she too could live with a no-deal outcome - though many around the summit in Salzburg do not believe that that is a credible threat.
"The French won the argument that the European Union has to come out more firmly against Chequers, and we see that in the Tusk statement that Chequers 'will not work.' I didn't expect that and I don't think the prime minister's office did, either".
Mrs May addressed EU27 leaders over wiener schnitzel with potatoes and Austrian wine, pitching her Chequers proposal before sit-down meetings begin on Thursday.
But Mr Raab insisted it was "the most credible plan" for Brexit, challenging critics by saying it was "a bit late in the day" for alternative proposals. "You can't belong to the single market if you are not part of the single market, but you can develop a lot of creativity to find practical, good, close solutions".
But she stood by the blueprint agreed by the Cabinet at her country residence in July as "the best way" to protect jobs in Britain and Europe and to avoid a hard border on the island of Ireland.
May insists that no prime minister can accept a different customs regime, a kind of border, within the United Kingdom, even as a backstop. May can not cherry-pick parts of the single market.
Reports suggested a tetchy meeting between May and Irish Prime Minister Leo Varadkar on the sidelines of the summit in Salzburg had helped harden views.
There are now six months to go until the official Brexit date, and as yet there isn't an exit deal.
That was originally viewed as the deadline, but Tusk confirmed on Wednesday he will seek approval from European Union leaders for a last-gasp Brexit gathering in mid-November. But Britain rejects the EU's proposal, which would keep Northern Ireland inside the bloc's customs union while the rest of the United Kingdom leaves.
May said she wanted to reassure people in Northern Ireland "that in the event of no deal, we will do everything in our power to prevent a return to a hard border".
British newspapers led their front pages with a Reuters picture showing May, attired in a red jacket, standing apparently aloof and alone from a mass of suited male European Union leaders.
May said that leaving with no deal remains an option. She said Britain "will be bringing forward our own proposals shortly" about how to break the impasse.