They are the masters now? Iain McNicol has resigned his post as Labour’s general secretary, clearing the way for a pukka Corbynite to take the role.

The writing had been on the wall for some time. Following Labour’s unexpected election advance, Labour party headquarters, McNicol and other senior officials faced heavy criticism, particularly in the leftwing blog Skwawkbox, for fighting an overly defensive campaign that cost the party seats. Skwawkbox is known to be both well-read and frequently briefed to by the leader’s office.

Also striking is the leader's office growing fondness for Friday night announcements: the leader's office quite likes to make its big moves quickly and unexpectedly on Friday nights after what they believe to have been a successful and effective refresh of the party's frontbench on 12 January.

Who will replace him? Although there is a comfortable “left” majority on the NEC that isn’t quite the same thing as a Corbynite one, and the internal politics of the trade union movement could yet complicate who the eventual general secretary is.

Jennie Formby and Andrew Murray, both Unite officials, are widely tipped for the post. Murray in particular is credited with helping to run the show during the general election campaign of 2017.

However, Unite are already well-represented on the party’s national executive committee and NEC officers group, not only through their direct representatives but because Diana Holland, the party’s treasurer, is a member of Unite. Labour’s other major unions may be reluctant to hand the post to Unite and it is arguably Unison’s “turn” (McNicol was linked to the GMB, while his predecessor, Ray Collins, was a member of Unite).

But Unite’s stock is high having pulled out the stops financially during the election campaign so the chances of a Unite official getting the post are higher than they otherwise would be, but I would also keep an eye on the likes of Samuel Tarry, the TSSA’s political officer with impeccable Corbynite credentials who helped run the 2016 leadership campaign.

I also wouldn’t rule out entirely the possibility that Corbyn will still end up getting his second-choice candidate. Don’t forget that McNicol wasn’t Ed Miliband’s preferred candidate in 2011. The important difference of course is that Miliband was in a very weak position in 2011 and Corbyn is in a very strong one in 2018. But while I would be surprised, it is still possible that the big trade unions will effectively bypass the leader’s office as far as choosing the next general secretary goes.