If May were to return to the Palace and inform the Queen that she could not, after all, form a government, the Queen would have to send for Corbyn and let him have a go. Likewise if she failed to get her Queen’s Speech through the Commons. But if she falls after that, because the government is in place, it would be correct for her to remain as caretaker while her party elects a new leader, whom the Queen would then send for. Corbyn would not get a look in.
It was therefore critical to the survival of the Tory government that May’s rumoured intention to resign on Friday morning was stopped by the senior members of the Cabinet and why they took control at that point. From then on May is doing their bidding, not the other way around and as soon as they have managed to get the government constitutionally on the road they plan to dump her. She was obliged to fire her two minders, without whom she is intellectually sterile, but to avoid her becoming dysfunctional, they allowed her old university chum, the amiable and emollient Damien Green, to be appointed First Secretary. Because he is an ardent Remainer they demanded she bring in a balancing high profile Brexiteer. May’s arch enemy, Michael Gove, the man who knifed Boris, made a surprise return. It is not clear whether Gove and Boris have made up and demanded his inclusion or whether May appointed Gove to shackle Boris.
Constitutionally May is now safe unless some new difficulty arises before the State Opening and the Queen’s Speech. She could fall if the Commons does not pass the Queens Speech, but after that she will go when the Cabinet decides. Because, although British Prime Ministers and Governments are possessed of extraordinary executive powers delegated by the Queen, these are conditional. Parliament has the power to sack the government by expressing no confidence in it, in which case the prime minister goes down too. But the Cabinet can lose confidence in the prime minister, in which case the incumbent goes but the government survives. As in the cases of Neville Chamberlain and Margaret Thatcher and in due course May herself.
If, through some circumstance not yet foreseen, May falls and Corbyn is sent for but cannot get a Labour Queen’s Speech through the Commons, there would be a general election. Labour would win it with a hefty majority. The Tories will do anything to avoid that happening until they have a new leader in place.
The issue of whether the the government can continue in its impartial role within the terms of the Good Friday Agreement if one of the parties against whom it may have to mediate, the DUP, is propping up the Tory party in office at Westminster, is political not constitutional. Any MP elected to parliament is constitutionally entitled to take part in government. The appropriateness of such action is political, as are the consequences, however unwelcome.
Finally the delusional May has now, I think, learned that it is not her government, as she said during the election in her I Me Mine campaign, but Her Majesty’s Government. The power of the Prime Minister is in the hands of the Cabinet and the power of the government is in the hands of the House of Commons. The power of the Commons is in the hands of the People. This she is now discovering. But it is too late. She is now politically neutered as all can see and in office only to keep the Tory party in power. It dare not return to the People until it has got rid of her.