One small, ultimately unsuccessful election promise by the National Party has thrown into disarray Auckland's plans for a fleet of versatile battery-electric trains.
Had the party made its pledge a week later, the $207 million plan would have been in the bag.
Instead, council agency Auckland Transport has just signed up to Plan B; buying 15 new electric trains costing $133m.
The agency will be scrambling over the next few weeks to resurrect the dominoes that fell in August, sweeping away its initial plan.
Auckland needs new trains by 2019 as patronage is rising stronger and for longer than expected, and the current fleet of 57 may be full or nearly full by then.
Plan A was cutting-edge hybrid trains. The extra battery power would allow trains to run beyond the end of the electrified network at Papakura to Pukekohe, currently served by ageing diesel shuttles.
This would directly connect Pukekohe nine years earlier than the official plan to extend electrification by around 2026.
The hybrids would have brought other advantages. They could potentially extend rail services beyond the western end of electrification at Swanson to Huapai.
Their battery power would help when the inner city rail loop (CRL) was being completed and hooked up to the western line at Mt Eden, avoiding a $10m-15m work-around to get trains through the site.
The $60m premium brought plenty of benefits and, in July, Auckland Council signed up for its half.
The board of the government's agency NZTA was due to do likewise in early August.
Council committee backed off after rail pledge
Five days before that board meeting, National announced that if elected, it would bring electrification to Pukekohe forward by perhaps three to four years.
With the upgrade gap to Pukekohe being shortened from perhaps nine years to five or so, NZTA's board backed off on the battery option.
And without their commitment to Plan A, Auckland Council's finance and policy committee had to reverse its earlier decision, and step back to match Plan B - 15 trains not 17, and no batteries.
What for a moment looked like a boon for Pukekohe's rail commuters is presently a bust. The diesel shuttle, the crossing the platform at Papakura, might go on until 2024 instead of 2019-2020.
Last night's purchase agreement couldn't be delayed. The Spanish trainmaker CAF has to get working if the trains - with or without batteries - are to start arriving when needed in 2019.
But Auckland Transport hasn't given up on Plan A - even though it believes the last possible date to include battery power in the order may be around Christmas.
Chief executive David Warburton told RNZ work was continuing with NZTA and the Crown on the case for the larger and more expensive hybrid train option.
Even if that failed, the agency could ask Auckland Council to consider paying a "bigger half" - covering all of the $60m or so premium, for two extra trains and battery power.
That could be a big ask with the pressure already building on the 10-year budget Auckland Council is starting to pull together for implementing next July.
And none of it would have been needed, if an election policy announcement heralding "good news" for Pukekohe, had been made a week later.