He said: “Let me get out there, let me take the mask off.
“As we come out of this, it allows the political space to open up, and allows me to open up.”
Asked if this was a pivotal moment for Labour, Sir Keir replied: “Yes – for me, for my party, this chance at the next election isn’t going to come again. We’ve lost four in a row. This is not about me, it’s about what’s right for our country.”
The hour-long, often intensely personal interview included contributions from friends and from Labour colleagues, including former Labour leader Neil Kinnock, who endorsed Sir Keir.
Mr Kinnock arguably restored the party’s electability after Michael Foot’s leadership in the Eighties.
He famously denounced the Trotskyist group Militant and other organisations from the far-Left.
While the former barrister has also tried to distance himself from the far-Left, unearthed reports reveal that in 1986, just after completing a postgraduate law degree in Oxford, Sir Keir was a member of the “editorial collective” which founded a radical left-wing journal called Socialist Alternatives.
The magazine was critical of the Labour party under Mr Kinnock, attacking the “Labour right’s hopeless neo-Keynesian economic programme” and called for a “radical alternative”.
In editorials, the magazine called for a “radical extension of common ownership over wealth and power”. In one, it argued that “prisoners should have much greater control over the conditions of their own imprisonment”.
Sir Keir used the platform to rail against “the authoritarian onslaught of Thatcherism”.
He then moved to Oxford for postgraduate studies.
In 2018, during an interview with the BBC’s Nick Robinson, he recalled going to Tony Benn’s house.
He said: “He let me sit in the Keir Hardie chair to interview him For Socialist Alternatives.”
A spokesperson for Sir Keir told The Times last year: “Keir is a proud socialist who has spent a lifetime fighting for justice and equality.
“He is standing in this leadership contest because of his determination to deliver a radical Labour Government at the next election.”