The Speaker of the House of Commons has delved deep into history and made a ruling that has significantly deepened the crisis facing Theresa May's government just days away from the official date of UK withdrawal from the European Union.
John Bercow invoked a convention from 1604 in his unexpected statement on Monday that essentially means the prime minister cannot bring her withdrawal agreement back to parliament unless it is substantially different from the package which was so comprehensively defeated on two previous occasions.
This bolt from the blue is very bad news for Mrs May who had pinned her hopes on persuading the DUP and sufficient numbers of Brexiteers to support her deal on the basis that defeat could potentially lead to Brexit not happening at all.
Whether or not the government is able to muster enough votes is certainly open to question although there is a sense that some Leavers, faced with the prospect of a lengthy delay, are prepared to soften their hardline stance.
We are told that yesterday's cabinet meeting was a fractious affair with no clear consensus emerging but we already know that this government is deeply divided, with ministers prepared to undermine the prime minister's authority safe in the knowledge that she is too weak to censure them.
It has been suggested that in order to get around the Speaker's ruling, this session of parliament could be ended early then reopened but, in practical terms alone, time is short.
The prime minister is due to write this week to European Council president Donald Tusk seeking a delay beyond the Brexit date of March 29.
Reports suggest Mrs May will ask for a lengthy extension to Article 50 while planning to bring her withdrawal agreement back to parliament.
Much depends on the mood of the EU27 who all must approve any delay.
It is difficult to predict just what will happen over the next couple of weeks or what further unforeseen twists, historical or otherwise, are in store.
