You can't be "hung by your own petard." A petard was a metal bomb filled with gunpowder. The saying is "hoist with your own petard." "Hoist" in that sense does not quite mean yanked up, as by a pulley. It's the variant past participle of a defunct verb "hoise" which possibly meant, in the sense above, blown sky high (or at least up into the air) by your own bomb. The phrase was famously used by Shakespeare in Hamlet. Hope this helps him who who is, sadly however, quite likely beyond all help.

The concept of that final Commons vote is a sham. There will be no split. Either all will vote yes to any deal or the whole thing will look so hopeless that the powers that be will recommend a vote against and all will follow. The people are watching, along with the Daily Mail, and the hard electoral realties will be casting their shadow over the whole charade. Long before then, what we need is for May, Corbyn, Cable and Sturgeon to lock themselves in a room and not emerge until they have produced a no-quibble joint statement thrashed out to the effect that, in the interests of this country, the brexit process will be halted forthwith, and including an agreement that there will be will a major push by the UK to start negotiations on the reform of the EU. We are far from alone in Europe in desiring that.