Interestingly..
If Boris doesn't comply with the Benn Act to call for a Brexit extension tonight, then the Scottish Court can send a letter, which carries the same legal weight as the PM sending it himself, to the EU asking for one.
So he's backed into a corner, but he can rightfully claim that he never asked for an extension himself.
If that's the case we can probably expect to see some anti Scotland rhetoric in the coming weeks, which will play into the hands of the Scottish Independence movement.
(Some 'little englander' MP's have a tendency to forget that the UK is made up of four nations and throw a hairy fit when it suddenly confronts them)