MPs will vote on the Grieve amendment which is effectively to protect the meaningful vote/see off attempt to dilute it.
If he wins then the Govt's attempt to dilute will have been defeated.
So effectively the Grieve vote is THE vote.
MPs can then try to vote to disapply standing orders but crucially it's up to Govt to make time for such a vote. Would they do that?
Prime Minister's spokesman this afternoon: "We will ensure that under standing orders the motion we bring forward is neutral."
The Govt controls if a vote on standing orders takes place.
You may have spotted the problem here.