He'll meet with Hamas and Sinn Fein – but a coffee with Chuka Umunna is a step too far for Jeremy Corbyn

High principles that go unchallenged when you’re cycling round a few far-left meeting halls are not fit for purpose when you intend to run the country

Like Brutus in Julius Caesar, to his supporters, Corbyn is an honourable man. And much like Brutus, he has often found himself in murderous company – whether he’s simply "attending without participating" in a controversial debate, or actively engaging with those whose position on the political spectrum could perhaps be described as more extreme than a Brian Blessed cameo in a Tarantino movie.

Perhaps the Labour leader's views on mingling with terrorists and their supporters have their merits in these insane times. In the 1980s, his meetings with Sinn Fein at a time when the Provisional IRA was still scattering bombs may have indirectly aided the Northern Ireland peace process. And though Corbyn speedily rescinded his fond description of Hamas as his "friends", many would agree that Palestine deserves support. Corbyn was always open to keeping a "back channel" to the Taliban ajar, too, and still believes there "has to be some route through somewhere" to what remains of Isis.

Many of us would see that "route" as akin to Mad Max Fury Road, but for peaceful Jezza it's worth taking because one day he might be served mint tea and cake in a sunlit tent.

But not, apparently, if Chuka Umunna is anywhere in the vicinity.

On Wednesday, Corbyn was invited to attend a cross-party meeting of leaders, convened by Theresa May, in an "attempt to chart a way forward" for her floundering Brexit negotiations. Yes, it was a bit of a last-minute copying-your-mate’s-homework-on-the-bus strategy, but according Umunna – invited as a spokesperson for The Independent Group of MPs which have broken away from Labour and the Tories – Corbyn will never know what actually took place in that room. For after he spotted his former colleague, Corbyn reportedly muttered "He's not a real party leader" and walked out. ("Flounced" has been suggested, but I rather imagine a peevish scuttle).

The Labour leader now blames "confusion" for his early exit – although if that was a valid excuse to leave, all of Britain would now be signed off work watching Homes Under the Hammer.

It seems to me that Corbyn is willing to engage with every variety of suicide-vest-happy, homophobic, freedom-loathing, misogynist dimwit with a grudge (and several who have a reasonable point but prefer to express it through explosions), and yet won’t breathe the same air as a bloke who dared to walk away from the Labour Party.

What’s harder to bear than a childish strop, though, is that Corbyn is now the only hope for millions in this benighted country. Yet from the very beginning of the Brexit process, leader of the Opposition has behaved like a sulky teen forced to visit his nan. We all know he never supported Remain, due to his view of the EU as a neo-liberal purgatory, but rather than admit it and clarify his position (which is effectively “strap in for socialist revolution, kids”) to allow a decent debate to be had, Corbyn has fudged and dissembled, sniped and muttered, and divided his own party to the extent that half is now briefing against the other and a handful are setting up a rival outfit.

High principles that go unchallenged when you’re cycling round a few far-left meeting halls are not fit for purpose when you intend to run the country.

I believe Corbyn could begin to undo the damage he has inflicted on British politics by extending the same understanding to rival parties that he extends to terrorists groups and, by opposing the government effectively, help to dig us out of this mess.

Although now, of course, it would be rather too little, too late.