Individual caucus members were asked in one-on-one meetings with their new leader who they voted for. According to party sources after responding to the question they were asked to pledge loyalty to the new leader
This is interesting in three ways. The first is that it was thought to be a good idea to ask MPs how they voted as you discuss their job prospects with them. The second is the request to pledge loyalty. The third is that it annoyed MPs enough that at least one of them is telling people about it.