Image copyright Reuters Image caption Labour's team including Shadow Brexit secretary Sir Keir Starmer have been negotiating with the government

"Constructive and detailed" - that sounds quite positive - Number 10's description of the talks today.

"Robust" - not quite so chirpy - Labour's use of political speak for what most of us might call a bit tricky.

"Disingenuous" - oh dear - a different Labour source's description of ministers' claim that what they were putting on the table in the cross-party talks today was something genuinely new on the vexed question of customs arrangements after we leave the EU.

As we reported this morning there didn't really seem to be much from the government that was concrete beyond what's already possible under the agreement that's been hammered out with Brussels.

The divorce deal and indeed yes, you guessed it, the backstop, both have forms of temporary customs unions in them to make trade between the UK and the EU easier.

Of course the precise language and mechanisms matter enormously.

But was there some big shiny new offer today? The short answer is: no.

And after hours of talks this afternoon, Labour sources suggest ministers in the end more or less admitted that in pointed discussions.

As we've talked about here before, the cross-party talks process is real.

Plenty of people in the Tory party hate it. Plenty of people in the Labour Party hate it.

But inside both leaders' camps, there is a genuine desire, more intense since they both had a bad night at the polls on Thursday, to see if they can sketch out a joint escape route from the mess of Brexit.

But the historically awful result for the prime minister does not seem to have shocked her into ditching her red lines - at least not yet.

It's important to understand this process is always unlikely to end up with some kind of joint defining pact - sources involved joke about the preposterous idea of some kind of May-Corbyn Rose Garden love-in - fond or awful memories of that summer's day when the Cameron-Clegg bromance was born in public (take your pick which).

The fact the talks have gone on for so long hint that there is serious merit in finding some kind of agreement on some kind of process.

At the very least senior figures in the government hope that the talks might mean Labour would allow the Brexit legislation to move on to its next phase.

In nerd terms, this is to allow the Withdrawal Bill to get through its so-called "second reading", knowing that at the next stage in Parliament where a committee of MPs would pore over every line, multiple layers of objections would be made, suggestions and changes put forward and then voted on, before finally, the bill would have its third reading, when MPs are able to give their final yes or no.

It is hard right now though to make a call on whether that is viable.

One former minister, experienced and not prone to make wild prediction, told me Number 10 was in "la la land" if they believed that could happen.

About half an hour later, another former and experienced minister told me they believe, in fact, it will fly and perhaps by the end of this month.

Whoever you ask, it is clear it is not straightforward.

So when the two teams sit down again on Wednesday afternoon, whether it is "constructive" or "robust", there's still an awful lot to do.