Then we have Boris. Clearly May benefitted from his decision not to stand. Was a dodgy deal done? I suspect it was. I also suspect May has carefully filleted the job, bringing in David Davis as Brexit Minister, in such a way that Boris is now effectively shafted. Brexit is the biggest Foreign policy issue. May has made clear that Boris isn't trusted to do such a difficult job. Davis is a hard line Eurosceptic, but has a decent grip of reality. He is also unlikely to be a potential rival. I suspect that May knows Boris is accident prone around foreigners and in this role, he's simply been given enough rope to hang himself, which given his previous record, shouldn't take too long.
In fact as I look down the list, it seems that all potential rivals have been either given a bullet(Gove), parked out of harms way or been set up to fail. It wouldn't surprise me at all, if Ms May already has her next cabinet reshuffle planned, before the ink has dried on this one.