There was something commendable yet eerie about the unity on display during this abrupt Greens leadership change. Richard Di Natale is taking charge of a party which always puts its own interests first, writes Annabel Crabb.

You have to say this for the Greens: They know how to keep a secret.

In most politicians' lives, party interests and public interests and personal interests swish about in a sudsy muddle, each surfacing in turn from time to time, each undeniably present beneath the surface.

For major party politicians, adversaries can be found everywhere, and those who sit next to you are often to be feared more than those who sit opposite; just look at the left wing of the ALP, which features some individuals - and always will - who'd rather move into a share house with Fred Nile than give each other the time of day.

The Greens party room know who their enemies in Parliament House are, and it's pretty simple: Everyone outside the door.

That's why they tend not to leak to journalists. That's why we only found out that Sarah Hanson-Young had challenged for the party's deputy leadership months after the event, when Bob Brown dropped the news offhandedly in a press conference. That's why, although it's obvious there was some pretty serious internal division within the party this year when it decided not to back the Government's planned increase to fuel excise, despite increased fuel taxes being a central part of the Greens policy platform, the exact details of the division are unclear.

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And that's why, when leader Christine Milne announced her resignation this morning (on Twitter, not planted with a sympathetic journalist, or set free via the party gossip-net) just about everyone was surprised.

Not all minor parties practise this kind of iron-clad discipline. The Democrats were a teeming Petri-dish of intrigue, rent constantly by horrid internal warfare. The Palmer United Party is a decreasingly-apt party name synonymous with abrupt storm-outs.

On one hand, iron-clad discipline is a good thing. Individuals don't waste excessive time on their own egos. When they're defeated internally, they tend to suck it up. And that means a lot less time bickering.

On the other hand, it's strange not to know where everyone stands. The abandonment of a central campaign platform item occurs, more or less seamlessly, and the lack of any evident fallout gives the whole thing a slightly eerie, unnerving air - like in Watership Down where the rabbits disappear and no-one says anything.

Today's result (a smiling Richard Di Natale elected unopposed to succeed Senator Milne; a pair of smiling and unopposed co-deputies in Larissa Waters and Scott Ludlam; former deputy Adam Bandt all smiles to be handing the job over) is lovely, but there's a whiff of Moscow about it.

Christine Milne entered the Greens leadership with minimum fuss and she leaves it in the same way. The predictions that were made when Bob Brown departed - that the party was a cult of personality built around him, that without his iconic presence the other senators would fall to petty bickering, that Milne herself was too pragmatic, that the stresses and strains of deal-making with the Labor Party in government would do for the Greens what the GST deal with the Liberals eventually did for the Democrats - proved collectively and separately off the mark.

This is partly to do with Labor, and the fact that that party of the Left can no longer straddle the widening divide between affluent inner-city progressives and further-flung Labor voters who rely on their cars.

But it's also to do with the fact the Greens put their party first. They put their party first when Kevin Rudd was shopping his emissions trading scheme, they put it first when signing deals with Julia Gillard, and they put it first in this first term Abbott Government, by denying the Coalition's agenda even when it accords with their own.

And they put it first today.

Annabel Crabb is the ABC's chief online political writer. She tweets at @annabelcrabb.