Several newspapers have reported in the last few minutes that Theresa May is now confirming that she will be prepared to withdraw the UK (and by extension Scotland) from the single market if the free movement of people is non-negotiable - which Angela Merkel and other European leaders have already stated is absolutely the case.
So this is the moment of truth for the unionist commentators who have spent months telling themselves that Nicola Sturgeon is bluffing about a second independence referendum. If they're right, Sturgeon will shortly abandon her red line that Scotland must stay in the single market, and will offer to settle for much more modest concessions.
I don't believe for one moment that she's going to do that. Deep down, I don't think her critics truly believe that she will either (except perhaps for a few based in London who are particularly poorly informed). Either way, it looks like we're about to find out.