I defy anyone not to be moved when the Labour leader opened up about the death of his mother who suffered from a rare condition called Still’s disease, which causes painful swellings in the joints.
When Morgan asked what he would have liked to say to his mother before she died, with tears in his eyes Sir Keir replied simply: “I love you.”
A lesson for us all perhaps to say those precious words to our loved ones before it is too late.
I am not cynical about the motivations of most politicians, which probably puts me out of step with many members of the public.
Yes, there are a fair number of charlatans, rogues and chancers on the take, probably more so than in many other professions.
But in my experience most politicians, and I’ve met a fair few over the years, are dedicated to public service and enter politics simply because they want to make the world a better place – and this holds true across the political spectrum.
Whether they are competent enough to tell the rest of us what to do and how to live our lives is an entirely different matter, and I am much more sceptical about that.
Now either Sir Keir is a consummate actor, which I think highly unlikely, or he came across in that TV interview exactly the way he is in real life, a fundamentally decent man who wants the best for his country.
What exactly he thought he was playing at when he was campaigning to put Jeremy Corbyn in Number 10 Downing Street 18 months ago is anybody’s guess.
These deeply personal, confessional style interviews are uncomfortable for me to watch.
I am old fashioned enough to think that some private things should stay exactly that – private.
And watching Sir Keir struggle to contain his emotions during that interview I kept thinking, why put yourself through that? After all, he had a hugely successful legal career before entering politics, rising to the post of Director of Public Prosecutions.
Why subject yourself to the stress, abuse and intrusion into your private life that comes with the thankless task of being Leader of Her Majesty’s Opposition?
I strongly suspect the answer is simple: he wants to make the world a better place and believes he can make a positive difference, and we should give him credit for that.
There was also a shrewd bit of political calculation going on, I suspect. Labour is consistently behind in the polls, largely thanks to the bounce the Conservatives have enjoyed thanks to the successful vaccine rollout, and Sir Keir is viewed by some voters as a bit robotic.
The Morgan interview was an attempt to humanise the Labour leader and show the warmth of his personality. It was a calculated risk but it paid off.
I believe that most people who watched that interview would have emerged with a more positive view of Sir Keir.
But the task facing him is a daunting one. The ship is sailing in the wrong direction and he has less than three years to turn it around. Labour have lost Scotland and show no signs of getting it back. And the obsession with trendy woke politics is alienating traditional Labour supporters across the Midlands and the North.
To add to his troubles the left of the party are in barely concealed revolt.
All eyes in the next few weeks will be on the Batley and Spen by-election on July 1, caused by the election of the sitting MP, Tracy Brabin, as the first mayor of West Yorkshire.
If Labour loses that, the left are threatening a coup to depose Sir Keir and replace him with a Corbyn clone. And if that happens Labour really are finished.
This is the scale of the task: in the 115 years since Keir Hardie, for whom Sir Keir was named after, founded the Labour Party there have been 23 leaders by my count.
Only three of them – Clement Attlee, Harold Wilson and Tony Blair – have gone on to win elections and become Prime Minister.
Whether Sir Keir joins the ranks of the rare winners, or the much larger number of losers, may be decided in the next four weeks.
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