I recently promoted somebody 'two levels up' and she is now managing her former supervisor. It was 100% the right decision; the new manager was already doing all of the managment work the supervisor was missing on. I communicated the news to both people (individually) before anything was announced and explained in some detail the reasons. I knew it would be disappointing news but got the reassurance 'i'll keep giving the same effort' etc. which was encouraging.
I could have handled the decision/communication better, I'm sure - the non-promoted person heard some of the reasons she was not promoted but I didn't reel off a list of failures when delivering news that was aleady poor; plus these were not news thanks to previous one-on-one meetings.
The problem: the passed over person is making life difficult for the new manager, obstructing, not responding to emails, declining meeting invites, etc. I was expecting a bit of a performance/motivation drop but not active hostility.
Thoughts on how to communicate that this isn't acceptable and needs to end quick? Other things I can do? This is related to the 'I am a former peer' podcast but didn't see others on the subject. I want to take the lead on this rather than expect the new manager to deal with it.