They called it Labour’s super Sunday, as prospective parliamentary candidates were chosen in the so-called defector seats (Nottingham East, Liverpool Wavertree), retirement vacancies (Bassetlaw, Poplar and Limehouse, Vauxhall and Blyth Valley), the Tory-held South Thanet, and Finchley and Golders Green, and the Lib Dem-held North Norfolk. You could say that every result bar Wavertree delivered surprises, though it would depend on how easily you are surprised.

In this context, remain versus lexit is no more than a contemporary gloss over a tug-of-war that has existed forever

In Bassetlaw, Sally Gimson beat candidates backed by Unite and Momentum, all the more unusual given that she’s a remainer in a leave area and not considered dyed-in-the-wool local. In Nottingham East, Nadia Whittome, an Another Europe is Possible activist, won with Unison and Aslef support.

Susan Dungworth won Blyth Valley against the candidate with overwhelming union and high-command support. Poplar and Limehouse was a battle between two Momentum figures, won by Apsana Begum. Ross Houston took Finchley and Golders Green, though whether it was as the staunchest remainer or the truest local that he beat the Momentum candidate is unclear. Rebecca Gordon-Nesbitt and Emma Corlett have been selected in South Thanet and North Norfolk respectively, though any Labour candidate will have a mountain to climb in those seats.

You could probably read in all these runes some message about Labour members and their remain sympathies. But in this context, remain versus lexit is no more than a contemporary gloss over a tug-of-war that has existed for ever between the local, constituency Labour parties (CLPs) and Labour HQ. If the leader’s office were to stay neutral and let the CLP decide, they would not only be relinquishing their control of the party’s composition, they would also be giving up their leverage with major unions, whose support is implicitly repaid with candidates of their own.

During the Blair years it would be rare for a candidate simply to be announced from on high. Rather, the party’s national executive committee would rig the shortlist and tip the hustings, so that by the time members arrived at the selection meeting, the chair would already have taken a call from the leader, explaining how beneficial it was for a certain candidate to be selected. The process was artificial to an embarrassing degree.

The selection system is founded on the basis that an MP is both local, ergo representative, and passionately, demonstrably loyal to the party, ergo the cream of the crop. So you’d have a man who’d been a Conservative until five minutes ago, or a Labour staffer whose connection to Stoke-on-Trent was that he could point to it on a map, performing laughable stances of ardent connection to the people of the area. Nobody liked it very much, but while the party was flying it didn’t seem to dent its vote share.

That power struggle hasn’t changed – how could it? But its execution today is very different, and its results are a lot less predictable. So, in Vauxhall on Sunday, roughly 400 members – including myself – turned up to a further education college in Clapham, south London, to choose between Katy Clark, the Unite candidate; Ibrahim Doğuş, the choice of the leader’s office; Stephen Beer, from Christians on the Left; Florence Eshalomi, her own candidate; and Claire Holland, the centrist’s choice.

Bear in mind that this constituency has had the painful experience of Kate Hoey as MP for 30 years, who is more Brexit party than Labour – and not just on Brexit itself, but in her entire sensibility. Only the power struggle within the membership – between a strong centre and a strong left, both sides too anxious that the other would prevail – protected her from being triggered decades ago. So there was a genuine air of hope and enthusiasm, a mood perhaps more united than in the other selections, since it was genuinely impossible to imagine anyone worse.

The NEC had explicitly rejected the local party’s expectation of an all-women shortlist, burning an awful lot of goodwill and losing a few solid candidates (Emily Wallace, Laura Parker) in the process, which can only have been to clear the way for a man. That man must have been Doğuş, because he sure as hell wasn’t Beer, who came over like a Tony Blair tribute act at a really eccentric wedding. However, this message had not percolated down very well; many Corbyn loyalists just assumed Clark was the leader’s candidate.

Each candidate did a stump speech, then was asked five identical questions: one on housing, to which they all delivered more or less the same supply-side fetish (“build more houses!”). There was one on science, which must have been intended to raise climate change, but actually yielded some bizarre perorations on robots and sexism and China. One on student fees and debt, in which most toed the party line. One on knife crime, and finally, a really contorted question on abortion, which can only have been to smoke out the faith element to see if it would be a problem down the line (Beer is Methodist, Eshalomi is Catholic).

Eshalomi shone as a human being: on any question related to people, she gave the real impression of having met some and thought about their predicament. She didn’t win outright on the first preference, but even those who understood and stuck to their faction (emphatically not everyone) had her as a second choice, which took her comfortably over the line.

The moral of these selections is that, if you want to stitch up a seat, you have to do it right. Any trace of bafflement leaves it all to the chemistry of the room, that perilous possibility that members might just vote for who they like the most. Who’s to say that the candidate whom members like, voters won’t like also? Perhaps it will play havoc with party unity down the line. But perhaps party unity is very last century.

• Zoe Williams is a Guardian columnist