"Tea apparently," the Prime Minister told the waitress. "English Breakfast, I think."
That was the innocent opening of his conversation - as the media were firmly ushered out on to the balcony.
One would expect that, under the scrutiny of about 40 reporters, photographers and camera operators, the carefully-orchestrated meeting between John Key and Act candidate John Banks would have been the most bland and banal of occasions.
But the potential disclosure of the contents of that conversation - held only a metre away from the closest reporters - could yet throw a rocket into this election campaign. It is a game-changer.
Elections, it should be said, bring out the best and the worst of politicians. There have been examples of inspiring rhetoric, intelligent debate and smart public scrutiny.
At the Helensville candidates' meeting at the Kaukapakapa Memorial Hall this week, seven candidates and nearly 50 locals debated issues ranging from euthanasia and school teacher performance to the democratic desirability of binding referenda.
The cup of tea at Cafe Urban in Newmarket was not such an occasion. Both Key and Banks will look back on it and acknowledge it was not their proudest political moment.
It started with an innocent mistake by a cameraman, unable to retrieve his radio microphone from the table as the media were herded out.
When he tried to get it back afterwards, one of Key's staff told him it had been handed to police. It hadn't occurred to him that it might have picked up the conversation - till he returned to his office and realised he had inadvertently recorded the conversation.
Key and Banks are not the first politicians to be tripped up in this silly way.
George W Bush famously told Tony Blair that it was time "to get Hizbollah to stop doing this shit". US deputy president Joe Biden told Barack Obama that his healthcare bill was a "a big f***ing deal". Then, last week, French president Nicolas Sarkozy was overheard telling Obama the Israeli Prime Minister was a "liar".
But it's the sheer range of comments in Key and Banks' discussion that is breathtaking - and the pair's assessment of the prospects of National, Act and NZ First.
Three years ago, Key's refusal to deal with Winston Peters was instrumental in forcing him out of Parliament.
Now, his deal-making may give the mercurial NZ First leader a foot back in. This will be grist to the mill for those who mistrust deals like those in Epsom and Ohariu-Belmont.
It's a pity - because most of our politicians are decent human beings.
Meeting them, spending time with them, breaking bread with the party leaders and their families, as the Herald on Sunday has been doing throughout the campaign, reveals that they can be warm, funny, real people, committed to making New Zealand a better place.
We saw that at Kaukapakapa, at the north end of Key's Helensville electorate this week. Seven candidates, and none of them afraid to answer questions candidly, put themselves on the line.
It's a pity Key missed it - he was too busy orchestrating his tactical cup of English Breakfast tea the next day.