The Hall of Mirrors in the Palace of Versailles is a fabled venue designed to showcase French power.

Dripping with gold, chandeliers and depictions of bloody victories, the room originally hosted French royalty and later, visiting dignitaries. It was also the venue for the signing of the historic agreement which ended the First World War.

This opulence could not be further removed from the horror on the ground in Ukraine as the leaders of the 27 member states of the European Union gathered in the room to consider the ramifications of the invasion.

The war has galvanised the EU into taking uncharacteristically swift decisions and breaching taboos on financing military weapons.

But at issue at the informal summit this week was the question of how far the EU was willing to go to support a country under attack in a war it has called "barbaric".

And Versailles is where the leaders drew the line. Before the summit, they had moved relatively quickly on incremental sanctions and agreed to allow all Ukrainian refugees easy access to work and live as EU citizens.

But Ukraine's request for fast-tracked membership was a bridge too far which fell foul on several fronts.

Many older member states are extremely reluctant to go anywhere on enlargement.

And several other countries are ahead of Ukraine in the queue and have pleaded to get out of the starting blocks.

In addition, complicated accession criteria have been hammered out through painful negotiation.

So the emotional plea made by President Volodymyr Zelensky directly to the European Parliament was rebuffed.

The direction was set by French President Emmanuel Macron on his arrival on Thursday when he said a country at war could not become a member.

French President Emmanuel Macron

But what happened inside the room on the first day, under the reflection of the 357 mirrors, is understood to have been a highly emotional debate.

Leaders gathered until 3am spending between three and four hours arguing about Ukraine’s request.

While they were always unlikely to fully agree to it, the question remained of the language the final declaration would use to address it.

Taoiseach Micheál Martin said he gave strong backing to the proposal from Ukraine and he said that support was echoed by some other eastern states including Lithuania.

"What came across last evening very strongly from those on the border of Ukraine, was they felt this message had to go out to those fighting in Ukraine. President Zelensky has said those people who are fighting now feel they are fighting for their children’s future and they want that future to be in a democratic Europe. And I felt it was a very emotionally compelling presentation, by quite a number of states - the Baltic states, Poland, Hungary and others on the border of Ukraine."

Taoiseach Micheál Martin arriving at Versailles

In the agreed text published late Thursday night, the EU acknowledged the "European aspirations and choice made by Ukraine".

It also referenced the factual position that the Council had invited the European Commission to submit its opinion on Ukraine’s application. This was done with unprecedented speed.

And it added: "The leaders undertook to further strengthen the bonds and deepen the partnership with Ukraine."

European Commission President Ursula Von Der Leyen with other EU leaders

While this does signal symbolic support, it is nowhere near a pathway to accession without even a reference to Ukraine becoming a candidate country.

And it demonstrated that while the EU has recently overcome its sluggish decision-making processes and displayed genuine unity, that unity has its limits.