[Margaret Pilkington]

I think that one of the main reasons why there has not been a formal challenge is that Jeremy Corbyn would(in the event of a leadership contest) be entitled to put himself on the ballot paper.
So it is not beyond reason that the grass roots could re-elect him as leader a second time.
This would cause humiliation for those MP's who have resigned from the shadow cabinet.....and those with the pack mentality.

I do not trust Tom Watson and would not put it past him to be making bullets for other labour MP's to be firing(though this is only my cynical and suspicious view.....and the only grounds I have for this suspicion is that when the brown stuff hit the fan, he distanced himself from the fallout by shaking his booty at Glastonbury - what an unedifying sight that must have been).