但即使是这一共识也并非铁板一块，因为它取决于谈判员首先是否能在另一个问题上达成共识：英国退出关税联盟后如何处理爱尔兰共和国和北爱尔兰之间的边界。
But even that agreement is not set in stone, as it depends on whether negotiators can first agree on what to do about the border between the Republic of Ireland and Northern Ireland once the UK leaves the customs union.