"I will be sitting in this office by 2027," the Prime Minister declared, joking that if our discussion went well, he might invite the interviewer into his official residence for another chat next year.
For a PM, there's never any time off for prime ministers. Just an hour before our chat started, Sir Keir had been on the phone with Ukraine's Volodymyr Zelensky and attempting to work out what on earth had occurred in Venezuela, where his key political chum, US President Donald Trump, had recently targeted and seized its leader, Nicolás Maduro.
Once our interview, which was considerably lengthier than usual, had finished, Maduro had been indicted in New York.
But as the new year begins, Starmer appears to have had something of a refresh. Maybe even just some downtime with his family at Chequers, the prime minister's country retreat.
That certainly appeared to have resulted in better spirits than at the sluggish end of 2025, a terrible year politically for him.
But are he and his colleagues being unrealistic if they believe his fortunes are set to improve?
The harsh reality for the prime minister is that a significant number of his fellow MPs are convinced he's ineffective at his job. A faction of them would rather take a risk and remove him sooner rather than later.
But Sir Keir was having none of it in the interview on Saturday morning.
Multiple times he told me he'd be "assessed at the poll", insisting nobody would remove his electoral mandate from him – despite the fact that the most effective strategy of halting Nigel Farage and Reform UK getting to No 10 might be for Labour to switch leader.
"We are in the struggle of our generation and I aim to lead us," he declared.
The issue for the PM is that he will be judged well ahead of then – in a huge set of elections in May throughout the UK. He sought to protest, maybe too much, that they are about who runs councils, and who runs the governments in Holyrood or Cardiff – and unrelated to Westminster.
Accurate – to some extent. But even though he may be reluctant to admit it, No 10 will be evaluated by those elections too.
This did not stop Sir Keir implying that there were no situation under which he would resign, should one of his colleagues challenged him for the job, should those elections be catastrophic for Labour.
He tried to rationalise his unpopularity by saying the public was naturally eager for things to get better. He sought to persuade the interviewer, and the public, that the coming months would be a change.
The economic situation would improve notwithstanding rising unemployment, he argued, when plans the government implemented during their first choppy year began to show results.
His core argument is that in 2026 the country will "see an improvement".
The PM may have spoken with renewed vitality than observed from him for a while – more relaxed, perhaps, with a longer slot to talk.
However, in spite of facing calls from within his own party for a more decisive strategy, with greater political clarity, more dynamism, more pace and more immediacy, his arguments were repeated ones.
Given that he is in considerable political peril, does he need a different script?
No administration, and especially not one that has been struggling in the polls for an extended period, gets everything its own way.
The Prime Minister's problems are not just because government is challenging, but because he and his team have erred, even in the recent past.
The PM expressed regret that he regretted saying he was "happy" to welcome back the Egyptian-British activist Alaa Abd El Fattah to the UK after an outcry when comments he'd made in the past – including calls for Zionists and police to be killed – came to light.
Starmer attributed it to "the process" for failing to identify what the activist had said before – a more diplomatic way of saying it wasn't his responsibility.
And he is inviting clear political dangers as the year unfolds. His alliance with the US president takes on a new jeopardy after Trump's strikes on Venezuela.
Based on years of interviewing Sir Keir Starmer, a former human rights lawyer who opposed the war in Iraq, over many years, the idea he would be content with these events seems implausible.
He told me he was a "lifelong champion of international law" but we "just lack the complete details at the moment".
Critics called for him to denounce it prior to we spoke. And the administration is expected to face more pressure to give an clear view in Parliament in the near future.
There has also consistently been bubbling pressure in the Labour party to revisit some of the outcomes of Brexit.
Sir Keir disputes he's doing that, but his new firmer commitment to integrate further with the single market – the giant economic European trading zone – will probably trigger howls that he is going back on his pledge never to try to reverse the decisions that flowed from Brexit.
A decision to cosy up to more of the single market will satisfy a faction on his backbenches, but it is prime ammunition for Reform and the Conservatives to
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