Mr Hurd will recommend the deal, so the first consequence of rejection could well be the resignation of the Foreign Secretary - and unfathomably dangerous consequences for John Major's administration. The threat is unspoken, but Mr Major's Cabinet is not in such a strong position that it can even risk losing one of its key assets. It would be the fourth resignation of a top Cabinet minister over Europe since Margaret Thatcher came to power and perhaps the most serious of them all.
Throughout the crisis, the stance of the Foreign Secretary on the issue has seemed more flexible than that of Mr Major. In his interview in the Guardian last week, the Prime Minister said that he could countenance delaying enlargement if it were necessary. Mr Hurd has always said that he regards this as a subject of great importance and that he does not wish to prevent it. The rejection of a deal will once more throw the EU into crisis, threatening not just its enlargement but its operation in every area. Crises like this crippled it for most of the period from the signature of the Maastricht treaty until the end of last year, when the ill-fated document was finally approved.
Enlargement was supposed to be a key part of Britain's agenda for Europe, expanding its borders to the east and north to bring in like-minded states. Many are now deeply concerned at the effect of delay and Mr Hurd was faced with their nervousness when he met their foreign ministers in Greece on Sunday. Previously, Britain had taken much of the credit for easing enlargement; a large part of that can now be written off.
Enlargement - the addition of four new member states, Sweden, Norway, Austria and Finland - will definitely be delayed, at least for six months, while officials try to unscramble the mess.
More worryingly, the rejection of such a key move will antagonise Britain's European partners yet further. In particular, enlargement is a key goal of Chancellor Helmut Kohl of Germany, Mr Major's conservative opposite number, with whom he has been trying - without much obvious success - to build a special relationship.
It is highly unlikely, if not impossible, that the other 11 member states will take drastic action against Britain, such as throwing it out; but there is no mechanism for such action.
However, there has long been a desire among some member states to proceed faster with political and economic integration. Britain could find itself left in the slow lane of a two-speed Europe, with integration shifting also to defence and security issues.Reuse content