"I will remain in this office by 2027," Starmer declared, joking that if the conversation proceeded smoothly, he might invite us into Downing Street for a follow-up talk in the coming year.
For a PM, there's never truly downtime for leaders. Just an hour before the interview began, the PM had been speaking with Ukrainian President Volodymyr Zelensky and attempting to understand precisely had happened in Venezuela, where his big political chum, US President Donald Trump, had just attacked and captured its leader, Nicolás Maduro.
By the time our lengthy talk, which was far more extended than normal, had concluded, Maduro had been formally accused in New York.
With the year commences, Starmer appears to have had something of a reboot. Maybe even just a bit of relaxation with the family at Chequers, the prime minister's country retreat.
This seemed to have left him in a more positive mood than at the sluggish conclusion of 2025, a terrible political year for him.
Yet, are he and his allies deluding themselves if they reckon his standing are poised to improve?
The grisly reality for the prime minister is that numerous of his party members are convinced he's underperforming at his job. Some of them would rather gamble and oust him sooner rather than later.
However Sir Keir was having none of it during our conversation on Saturday morning.
On several occasions he told me he'd be "evaluated at the poll", maintaining nobody would remove his five-year mandate from him – despite the fact that the best chance of stopping Nigel Farage and Reform UK entering No 10 might be for Labour to switch leader.
"We are in the fight of our times and I intend to lead us," he declared.
The issue for the PM is that he will be judged far sooner than then – in a major set of elections in May across the UK. He tried to protest, perhaps too much, that they are about who runs councils, and who runs the devolved administrations in Holyrood or Cardiff – and unrelated to Westminster.
True – to some extent. But even though he may not want to admit it, No 10 will be judged by those elections too.
This did not stop Sir Keir stating that there were no situation under which he would step down, even if a his colleagues challenged him for the job, should those elections prove catastrophic for Labour.
He attempted to explain his low poll ratings by saying the electorate was naturally impatient for things to change. He tried to persuade the interviewer, and the public, that the coming months would be different.
The economy would strengthen despite rising unemployment, he said, when policies the administration enacted during their initial turbulent year began to take effect.
His core message is that soon the country will "turn the corner".
The prime minister may have communicated with more energy than observed from him for a while – calmer, perhaps, with a longer slot to talk.
However, in spite of facing pressure from many directions for a bolder approach, with greater political direction, more vigour, more speed and more urgency, his arguments were repeated ones.
When he finds himself in such significant political trouble, should he consider a change of tack?
No government, and certainly not one that has been struggling in the polls for many months, has everything its as desired.
The Prime Minister's problems are not just because governing is hard, but because he and his colleagues have erred, even in the recent past.
The prime minister expressed regret that he was sorry for saying he was "pleased" to welcome back the Egyptian-British activist Alaa Abd El Fattah to the UK after an backlash when past remarks he'd made in the past – such as calls for Zionists and police to be killed – surfaced.
Starmer attributed it to "the system" for not realising what the activist had said before – a fancier way of saying it wasn't his responsibility.
And he is facing clear political risks as the year gets going. His alliance with the US president takes on a new risk after Trump's military action on Venezuela.
Having interviewed Sir Keir Starmer, a ex- human rights lawyer who opposed the war in Iraq, over a long period, the thought he would be at ease with these events seems implausible.
He asserted he was a "lifelong advocate of international law" but we "simply haven't got the complete details at the moment".
Some called for him to condemn it prior to we spoke. And the government is expected to face more pressure to give an definitive view in Parliament in the coming days.
There has also consistently been bubbling tension in the Labour ranks to undo or remake some of the outcomes of Brexit.
The PM denies he's heading in that direction, but his new firmer pledge to integrate further with the European trading bloc – the giant economic European trading zone – will probably provoke protests that he is reneging on his vow never to try to reverse the choices that followed Brexit.
A commitment to cosy up to more of the single market will delight some on his backbenches, but it is easy fodder for Reform and the Conservatives to
Elena Verhoeven is a tech enthusiast and digital strategist with over a decade of experience in emerging technologies and online innovation.