Tommy Sheridan has been convicted of perjury and will now probably go to jail. The imprisonment of Sheridan was the only plausible result of this perjury trial. It was undoubtedly the one sought by police and by News of the World. It may not have been the result sought by members of the Scottish Socialist Party (SSP) who helped to instigate the perjury case. And those who leaked and sold materials to the press may not have had prison in mind. But it is the logical and necessary result of their actions, and their vociferous expressions of relief at the verdict are notable. And it is a setback for the Scottish Left. To speak frankly, I do not see the SSP having much of a role in its repair, for all that it contains some immensely talented, charming and principled people.

The SSP was once the envy of the radical left. A thriving model of socialist unity in action. It was based significantly, perhaps too significantly, on the personal credentials of Tommy Sheridan, whose inspiring lead in resistance to the Poll Tax first gave him the stature he subsequently enjoyed. It was natural that when the tabloid press came after the SSP, they would focus on Sheridan. And as they could not attack him for his politics - or at least if they did it would make little difference - they tried to attack him over his personal life, his sexual conduct. Sheridan's response was to initiate libel proceedings. I think most of his defenders consider that this was a crazy thing to have done - the bourgeois courts are a risky terrain for socialists, in which the odds are almost always stacked against you. Nonetheless, he won the support of the majority of the party for his position, which was that the attack on Sheridan was an attack on the party. But the SSP executive panicked, forced him to resign as national convenor and indicated that they would not support him in his libel case.

As it transpired, not only did they not give him broad backing, they agreed to testify for News of the World. In justification, they claimed that Tommy Sheridan had no right to sue for libel because the allegations were true. They argued that he had no right to expect them to lie for him, and that he was putting his ego and his reputation ahead of the fortunes of the socialist left. But, even assuming that every word of the News of the World's claims were true (an assumption which I am only prepared to entertain for the sake of argument), and even if you believed that Sheridan's libel prosecution was a mistake, to actively assist the News of the World in court was not only unnecessary but self-destructive. It meant that, as witnesses on oath, they had an interest in seeing Sheridan lose and the Murdoch press win. It was always clear that a large part of the Left would consider this unforgiveable behaviour, a form of political scabbing, and that such actions would tear the hitherto united and growing socialist left in twain (twain at the very least). It is also now known, as a result of this perjury trial, that in addition to testifying for Murdoch, leading SSP member Alan McCombes secretly went to the Sunday Herald with a 'sworn affidavit' three days after Sheridan was deposed as party convenor, stating that if Sheridan had not resigned they would have "put certain information into the public domain which would have forced him to resign". This wasn't just comrades put in a difficult position. From the second the anti-Sheridan faction coagulated in the SSP executive, it pursued its quarry ruthlessly - a point that becomes more clear as time goes on.

When Sheridan won his libel case, the News of the World was out for blood. But the anti-Sheridan faction in the SSP was also overwrought. They immediately went on the offensive. In the wake of the case, numerous leading SSP members suddenly publicised their view that sexism had been rife in the SSP - though they had apparently failed to act on this belief until then. A former SSP activist wrote in The Guardian that the issue was about gender rather than class, and that Sheridan's victory was a victory for machismo. She alleged that Sheridan had used misogynistic language about SSP members, describing them as a "cabal of women". This misrepresented, perhaps intentionally, an open letter from Sheridan to members of the SSP which used the phrase "cabal of comrades". But it contributed to a political mythology, which is still propagated to this day, and which casts Sheridan as a misogynist.

And this has remained an important part of the SSP's rationalisations for their methods. The current issue of Scottish Socialist Youth, for example, revels in Sheridan's conviction and depicts him as a "mad shagger", and the sex clubs he allegedly visited as tantamount to brothels - thus he is characterised as a macho prick, availing himself of (what some would see as) some of the worst forms of female oppression. Just one point about this. If it is indeed the case that Sheridan's alleged actions mark him out as a chauvinist, then it is time for SSP members and apologists to stop pretending that the allegations against him were solely to do with personal morality and thus not at all to do with the politics of the SSP. By their own account, the allegations were definitely political, and definitely damaging to the SSP.

But this sort of narrative re-framing would be no more than natural behaviour among people who had allowed personal bitterness to overtake their political judgment and made quite a few angry opponents of former supporters in the process. At this point, with News of the World beaten, Sheridan and his supporters took it as a good time to vacate the remnants of the once great and now greatly reduced SSP. What then happened defies belief. Members of the SSP conspired to instigate a perjury prosecution, by bringing materials to the police and the media (for a considerable sum of money, naturally) that would incriminate Sheridan.

George McNeilage either recorded a private conversation and sold it to News of the World for £200,000, or he participated in a fake intended to implicate Sheridan in perjury, and sold it to News of the World for £200,000. Then Barbara Scott produced a handwritten minute of unusual detail, which many members of the executive of the time don't recall seeing before, from a meeting which purportedly proved that Sheridan lied, and marched down to the local constabulary of the Lothian and Borders police with that minute. The invocation of principle in a case like this can be dangerous. But I like to think that I know an issue of principle when I see it, and I think on principle it is aborrent and reprehensible to make yourself a police informant or sell a former comrade to the newspapers, even for the sake of something as important as a factional vendetta.

A prosecution was initiated. Once again, leading SSP members bore witness, but this time for the prosecution. Of 42 prosecution witnesses, 24 were SSP members, 16 from the original executive. Were it not for this footage, those minutes, and that testimony, Tommy Sheridan would be a free man. Were it not for a this extraordinary factionalism, the News of the World and Lothian and Borders police could not have hounded and persecuted Sheridan and his wife. He is now expected to go to prison.

This is a setback, as I said. Anyone who believes otherwise is not living in the real world. But Scotland also saw one of the biggest protests against the cuts after the comprehensive spending review. It is going to be at the forefront of resistance to Tory austerity. And if the major electoral vehicle for the Scottish radical left now lies in tatters, its former star now heading to jail, there will be ample opportunity to rebuild the Left. And in that future Left, I do see a role for Tommy Sheridan.