IT all comes down to a matter of trust.

Nicola Sturgeon admitted as much as she emerged from the famous black door in Downing Street to address the waiting media.

Expectations before the latest JMC were not high; indeed, both governments had lowered expectations of a breakthrough.

But the First Minister said while the differences between her and Theresa May were not insignificant, nor were they “insurmountable”.

Indeed, she explained with a deal of determination, a deal could be done.

Now, given the overall political context of the day - the Russia crisis on which the SNP leadership expressed full support for the Prime Minister’s stance - it would have seemed churlish for Ms Sturgeon to stoke the constitutional fire; there will be other occasions to do that.

And it is difficult to see how either government can fudge what each regards as a principled position on the Brexit Bill.

But the FM hit the nub of the matter when she said the impasse centred on Whitehall allowing Holyrood to “consent” to changes to devolved powers, noting how if did that, then Mrs May and her colleagues would not find Holyrood withholding such consent “unreasonably”.

“There is discussion to be had to give assurances that wouldn't be the case," noted Ms Sturgeon.

Allowing the Nationalist Government a veto on what the Tory Government could do and relying on the reasonableness of the SNP leadership might prove rather difficult for Mrs May and her Conservative chums.

So despite the FM’s unexpectedly warm words, this constitutional conundrum might still prove impossible to crack.