As cars lined up in the rain outside London’s Lancaster House, the diplomats gathered within sipped wine and sought intelligence on where Brexit is headed at the Foreign Office Christmas party.
Theresa May’s senior team are wrestling with the same question: What should she do if her deal is thrown out? In private, the options on the table are dramatic and include postponing the divorce from the European Union, calling another referendum or even announcing fresh national elections.
In under 100 days, the U.K. is due to leave the EU, fulfilling the mandate of the 2016 referendum and marking the culmination of

