Hammond talking Brexit
It goes without saying that they shouldn't show their hand. Theresa May has been saying the same thing for weeks.
The flipside of the argument is that the public should have a right to know (and argue against) certain concessions.
The red line is immigration, it seems, with Hammond saying the UK can't accept uncontrolled free movement of people.
Ultimately, I think that's what it will boil down to and that trade will essentially be unchanged. By the time Europe is at the table, they bad blood over the vote will have died down and there will be no appetite to punish Britain via trade (which would also be punishing themselves). Then again, if they give Britain too good of a deal, it won't be long before someone else is holding a referendum.