This story provides an interesting insight into the mindset of the British Brexit negotiators and IMO gives a clear "tell" that no doubt the wily EU negotiators will use:
http://www.bbc.co.uk/news/world-europe-39915364
It seems that David Davis wants to make a trade deal the number one priority of the Brexit discussions and is willing to put matters of border security into a second round of negotiations.
IMO this smacks of desperation on the part of the British team. They need a trade deal to wave in front of the British public to reassure everyone that it's all going to be fine. My concern is that in their haste to get such a deal, they'll leave important points unresolved and, more importantly, antagonise the EU unnecessarily.