When one of your interlocutors, with whom you are negotiating, comes to you on a separate matter and demands payment (£44 million) and concessions (more migrants) to which you quickly agree - and then feels able to tell you, by the way - on the main issue that you are not going to get what you want, I think it's pretty clear who is in charge.
Such is the position we find ourselves with France and the Le Touquet agreement (HERE). Mrs May has given France pretty much what it wants, the alternative being the return of the border to UK soil. President Macron felt quite able to tell us their will be no access to the single market for UK based financial services unless we pay into EU funds and accept ECJ rulings (HERE).
We have now conceded on the sequencing of talks, on the Brexit bill, on the role of the ECJ and on the need for a transition period. Soon we will be making concessions on the nature of the transition. We will agree a continuation of the status quo including the continuation of free movement and the right of immigrants to bring in relatives after we leave.
I wonder when the Brextremists will finally realise we are the supplicant, not only in the withdrawal and transition negotiations but in the coming trade negotiations. And this will also be the case when we start to try and grandfather the existing EU trade deals and negotiate new ones with the USA, China and India. Every nation in the world will realise how desperate we are to put trade deals in place as soon as possible and will negotiate accordingly. This is how the world works.
The EU is slow to agree trade deals because like the USA and China and India, they are big enough to know their market is an attractive and valuable space. They can all survive without trade deals and therefore can wait until the smaller, weaker party comes back. So it will be with us.