"I will remain in the same office by 2027," the Prime Minister stated, joking that if our interview went well, he might invite us into his official residence for a follow-up talk in the coming year.
There is never any downtime for those in the top job. Shortly before our chat started, Sir Keir had been in calls with Ukraine's Volodymyr Zelensky and trying to decipher exactly what had transpired in Venezuela, where his close ally, US President Donald Trump, had recently targeted and seized its leader, NicolĂ¡s Maduro.
By the time our lengthy talk, which was considerably lengthier than typical, had ended, Maduro had been indicted in New York.
With the year commences, the Prime Minister seems to have had a degree of a refresh. Perhaps even just a little relaxation with the family at Chequers, the prime minister's rural getaway.
This seemed to have resulted in improved morale than at the saggy end of 2025, a terrible annus horribilis for him.
Yet, are he and his supporters being unrealistic if they think his fortunes are set to get better?
The harsh truth for the prime minister is that numerous of his colleagues are convinced he's ineffective at his job. Some of them would sooner gamble and remove him in 2026.
But Sir Keir was dismissing such talk during our conversation on Saturday morning.
Repeatedly he told me he'd be "evaluated at the poll", arguing nobody would take his electoral mandate from him – even if the most effective strategy of stopping Nigel Farage and Reform UK entering No 10 could be for Labour to change leader.
"This is the fight of our lifetime and I aim to lead us," he affirmed.
The issue for the prime minister is that he will be scrutinised far sooner than then – in a huge set of elections in May throughout the UK. He sought to contend, perhaps excessively, that they are about who runs councils, and who runs the governments in Holyrood or Cardiff – and not about Westminster.
True – up to a point. But although he may be reluctant to admit it, No 10 will be evaluated by those elections too.
This did not stop Sir Keir suggesting that there were no scenario under which he would step down, even if a his colleagues contested his leadership for the job, if those elections prove disastrous for Labour.
He attempted to rationalise his low poll ratings by saying the public was reasonably anxious for things to get better. He aimed to assure the interviewer, and the nation, that the coming months would be a change.
The economy would improve in the face of rising unemployment, he claimed, when strategies the government enacted during their initial turbulent year began to show results.
His core message is that in 2026 the country will "turn the corner".
The prime minister may have spoken with greater vigour than observed from him for a while – less tense, perhaps, with a longer slot to talk.
However, in spite of encountering pressure from many directions for a more decisive strategy, with greater political vision, more vigour, more speed and more immediacy, his points were repeated ones.
When he finds himself in such significant political trouble, does he need a new narrative?
No administration, and certainly not one that has been struggling in the polls for an extended period, gets everything its as desired.
The Prime Minister's problems are not only because government is hard, but because he and his team have erred, including in the last few weeks.
The PM expressed regret that he regretted saying he was "pleased" to welcome back the Egyptian-British activist Alaa Abd El Fattah to the UK after an controversy when past remarks he'd made in the past – including calls for Zionists and police to be killed – resurfaced.
Starmer blamed "the system" for failing to identify what the activist had said before – a fancier way of saying not my fault.
And he is inviting evident political dangers as the year unfolds. His close relationship with the US president entails a new complication after Trump's military action on Venezuela.
Based on years of interviewing Sir Keir Starmer, a ex- human rights lawyer who opposed the war in Iraq, over his career, the thought he would be comfortable with such action seems far-fetched.
He asserted he was a "career-long champion of international law" but we "simply do not have the full picture at the moment".
Critics called for him to denounce it before we spoke. And the government is likely to face increased demands to give an clear view in Parliament in the near future.
There has also long been growing tension in the Labour ranks to reverse or renegotiate some of the consequences of Brexit.
Sir Keir disputes he's pursuing that, but his new specific pledge to integrate further with the European trading bloc – the huge economic European trading zone – will probably elicit howls that he is breaking his promise never to try to undo the decisions that flowed from Brexit.
A decision to integrate into more of the single market will please many on his side of the party, but it is prime ammunition for Reform and the Conservatives to