As militant Trotskyists committed to the overthrow of capitalism go, Colin Fox is a lovely bloke.

The 56-year-old is a mainstay of the Left in Scotland but, unlike too many of his comrades, he is gifted with a sense of humour.

I have yet to encounter anyone in my profession who has a bad word to say about him -- "good guy" and "principled" are the terms that come up most often -- and even politicians from parties he rails against as "neoliberal" and "reactionary" hold him in warm regard.

This is an achievement all the more remarkable given his role in the bitter split in the far-left that followed the tumbling from grace of Tommy Sheridan. The fallout cost Fox his seat in Holyrood at the 2007 election but he continued as the respectable face of the Left in Scotland.

A cynic might misread Fox's popularity as proof of weakness or insufficient ideological dedication. To the contrary, it is his unflagging pursuit of an unrewarding cause, one that he nonetheless believes in profoundly, that inspires admiration.

Had he bitten his lip and done as he was told, Fox could have made a nice living as a Labour MP; instead he chose Scotland's radical Left and has given it his all, even when it didn't deserve even a tenth of the effort.

He presents himself in this election under the banner of Rise, a post-referendum coalition of socialist Yes campaigners, many of whom were involved in the impressive Radical Independence Campaign, and others affiliated to the Scottish Socialist Party (SSP), for which Fox remains national spokesperson.

"Rise is a project to pull the Left together," he explains to me. "Tony Benn used to say, 'There's too many socialist parties and not enough socialists'. This is a left-unity project to try to pull all the Left into one alliance."

Which sounds eminently sensible but what was wrong with the SSP? It may not have been young and shiny and half its members might not have columns in the National but it stood for recognisable things. Try explaining to my dad, an SSP second-voter for some time now, about harnessing the energy of National Collective and the Common Weal and he'll look at you askance. What's that got to do with renationalising the railways and the energy companies and making sure working folk have decent homes and pay packets and union rights? Bread and roses, not bread and wish trees.

Fox is adamant that a union between the various elements of the Yes-left was essential.

He says: "The SSP was involved for the two previous years in the Yes campaign. We were involved in a much broader alliance, involving people in the Radical Independence Campaign and the rest of the Yes campaign. We thought we'd try to present a broader alliance this time than just the Scottish Socialist Party."

The election of Jeremy Corbyn as Labour leader has convulsed the political world; all for the better, say his enthusiasts; to the detriment of the Labour Party, say his critics. What can't be denied is that Corbyn is the most left-wing leader in Labour's history. Doesn't this rob hard-left parties like Rise of their raison d'etre?

Fox is defiant: "I know Jeremy Corbyn. I've known him for a long time. I have a tremendous regard for him... He's a socialist. He doesn't support independence, though. And though he's the leader of the Labour Party, I don't regard the Labour Party as a socialist party.

"Everybody looks at Jeremy Corbyn, especially from my perspective, and wishes him the best of luck but that's because he's going to need it. The great trouble the Labour Party has is that nobody knows what it stands for anymore and Jeremy Corbyn is a manifestation of that crisis.

"How many MPs support Jeremy Corbyn? I dare say I have more support for Jeremy Corbyn than 95% of the parliamentary Labour party. I'm comforted by the fact that socialist ideas are mainstream in Scotland and that is why the SNP pretends to be a socialist party and the Labour Party pretends to be a socialist party with a new socialist leader. Of course, they're not.

"Socialism is a clearly defined critique of the free market. Socialists, for example, for the past ten years have flagged up how deleterious the privatisation of our schools and hospitals has been under the private finance initiative. Remember, that was a Tory idea that Labour implemented and the SNP used under the Scottish Futures Trust.

"There's a good example: Socialists would never privatise public assets. We want to see them improved. Goodness knows they need it. These parties privatise and claim that they're socialist. They redistribute wealth to the rich and claim that they're socialist. These inconsistencies are shown up in the end."

His new Rise coalition is clear about what it wants and when it wants it, Fox assures me. "Socialists believe in replacing capitalism with a better system in terms of economics and human relations. The difference between Rise is we want that now, the Labour Party wants it in a thousand years, and the SNP -- I don't know if they want it at all."

All of this will come as unpleasant news to those in the SNP and Labour who believe their party to be the standard bearer of authentic socialism.

It's not a case of traducing his opponents for Fox, just allowing them to be honest about what they really believe. He insists: "I know Nicola Sturgeon quite well. I sat with her on the Yes advisory board for two years. Nicola doesn't describe herself as a socialist. Alex Salmond doesn't describe himself as a socialist. I respect them because they know they aren't. What Rise is about is saying: These are what socialist ideas are: Public ownership. Redistribution of wealth. Anti-imperialism. Intervention in the economy."

Of course, one of the reasons the SNP can pass itself off as socialist (in Pollok, mind you; in Perth it's more, "another scone, minister?") is that people like Fox provided cover during the referendum. Instead of campaigning separately, he worked at the heart of Yes Scotland, an outfit independent of the SNP in the same way that the Angels were independent of Charlie. It's hardly surprising the SNP is still trading on the lefty kudos that brought them and Rise can't object after the fact. You gotta dance with the one what brung you.

No one could accuse Rise of inauthenticity. Its manifesto calls for a 60p top rate of tax, 100,000 green jobs, 100,000 council and social rented homes, a £10-an-hour national minimum wage, a £100,000 salary cap, and a second referendum on independence.

That's a bold socialist prospect-- No, no. Wait a minute. We have to get into this.

Like so many on the Left, Fox embraces independence as the route to socialism north of the border. Why though? Why are so many from a movement attuned like few others to the dangers of bourgeois nationalism merrily linking arms with flag-waving capitalists?

Fox insists he is not a nationalist: "Lenin wrote about the right of nations to self-determination being a democratic question and it is. It's fundamentally about the democratic right to plot your own destiny and your own future. It doesn't make you a Scottish nationalist if you support independence."

Hmmm... Sceptical pug is sceptical.

After all, Lenin also wrote: "The class-conscious workers fight hard against every kind of nationalism, both the crude, violent, Black-Hundred nationalism, and that most refined nationalism which preaches the equality of nations together." The ease with which so many on the Scottish Left have parked their internationalism -- no solidarity until Scotland gets to issue its own passports! -- is at best naive, at worst hypocritical. Under independence, there will be poverty in Leith and poverty in Liverpool but we will care more about one than the other. If that's socialism, it's got less inspiring of late.

Fox's critique is rooted in history and, whether I like it or not, I suspect history will prove to be on his side.

"I grew up in Motherwell in the 1980s. My grandfathers wer e both steelworkers with the British Steel Corporation. My phone was supplied by British Telecom. I went to work on British Rail trains. My mum worked for the British National Health Service. I voted for the British Labour Party. In opinion poll after opinion poll, youngsters like me growing up in Motherwell described themselves as British. Our grandparents had fought in the British Army in the Second World War.

"Life has moved on. In 2016, people consider themselves Scottish and not British. So we have to reflect those changes."

That strikes me as a highly practical but self-evidently nationalist position. Even the principled Left can't escape the trap of Scottish moral superiority: Every flag in the world stands for reaction except the Saltire, the revolutionary emblem of our low-tax socialist paradise.

I could talk to Colin Fox about socialism or nationalism or pretty much anything all day long. My old fella might take Rise for a bewildering bunch of teenagers but in Fox they have a serious and substantial figure. If they fail to register in this election, a period of critical introspection would be in order. Is fastening the national question to the centre of their platform advancing anything more than the SNP's political ambitions?

The Nationalists got 56 seats at Westminster, another majority at Holyrood and they get to decide the pace of travel towards a second referendum. What did the Left get out of it? If socialists cannot prosper until independence -- at some future date to be determined by Nicola Sturgeon's pollsters -- it might lead some to reassess matters. Maybe it's time to stop dancing with the one what brung you and start cutting some moves of your own.

Stephen Daisley is STV's digital politics and comment editor. You can contact him at stephen.daisley@stv.tv.