Media playback is unsupported on your device Media caption Donald Tusk: "Special place in hell" for those without Brexit plan

They weren't off-the-cuff remarks, but a planned outburst.

The softly-spoken politician who holds the authority of all EU countries has just completely condemned a chunk of the British cabinet, wondering aloud: "What that special place in hell looks like for those who promoted Brexit, without even a sketch of a plan how to carry it out safely".

Sure, for a long time the EU has been frustrated with how the UK has approached all of this.

And sure, plenty of voters in the UK are annoyed too at how politicians have been handling these negotiations.

But it is quite something for Donald Tusk to have gone in like this, studs up, even though he sometimes reminisces about his time as a football hooligan in his youth.

Be clear, he was not intending to talk about voters who wanted to Leave, but politicians who were involved in the campaign.

He also had pretty stern remarks for those who'd been on the other side of the argument, accusing those who still want the UK to stay in the EU of having "no political force, and no effective leadership".

Mr Tusk will be all too aware that he will provoke tempers at home, even laughing about it as he left the stage with the Taoiseach, the Irish leader, Leo Varadkar.

But if you strip away the planned flash of temper, also in his remarks was an invitation to the prime minister to come forward with a different version of the backstop - a "believable guarantee", a promise that a "common solution is possible".

That is, on the face of it, in tone at least, more of an opening to the UK to put something new on the table than we have seen from the EU side.

Certainly, Theresa May's most pressing job is to put something that could work on the table in Belfast, and in Brussels, and to do it fast.

But don't forget, also at her back, she has Brexiteers whom she needs to manage, whose expectations she needs to contain, whose votes she desperately needs.

And at a time when cool tempers and compromise are absolutely needed, Mr Tusk's remarks are likely to whip up the mood instead.