Green leader Zack Polanski has been reported to the police over a social-media post. On Monday, Polanski shared a photograph on his Instagram page. It featured a bearded oddball at a Green Party event, wearing a t-shirt depicting a guillotine, above which are the words: ‘We’re only making plans for Nigel.’

Soon after, Reform UK leader Nigel Farage tweeted a screenshot of Polanski’s post. ‘If I was to post anything as inciteful’, he wrote on X, ‘then I would expect to be arrested, and so should Polanski’. Zia Yusuf, Reform’s spokesman for home affairs, claimed that by sharing the image with his 713,000 Instagram followers, ‘Polanski is inciting murder. It must be treated as such by the police.’

It now seems as if the police are doing just that. The Metropolitan Police confirmed last night that they had received a ‘third-party report’ relating to an ‘image shared on social media’ and that officers have been ‘conducting enquiries into the matter’. Polanski’s post has since been deleted, and the Green Party has said that he ‘unequivocally does not support this dangerous message’.

There is no doubt that the t-shirt and the Instagram post were in the worst possible taste – especially so soon after the appalling murder of Reform member Ann Widdecombe. But does that mean Polanski’s post was – or should be – a crime?

The UK has strict laws against incitement to violence. But prosecution on these grounds normally requires that the person making a remark genuinely believes that his or her words will result in immediate violence. A tasteless t-shirt would not normally meet the criminal threshold, and nor should it.

What’s more, Polanski did not take the photograph himself – he was tagged as a collaborator in a post containing 20 images. He appears to have shared this without noticing the offending picture. That a Green supporter would proudly pose in such a t-shirt certainly says a lot about the rot in the heart of Polanski’s party. But again, this is no reason to treat this as a criminal matter.

Where Farage is on more solid ground is his complaint about the media’s response to Polanski’s post. As he stated, if he had posted a similar image about, well, anyone, the mainstream media would go bananas. His political career would be over. He would probably be arrested, too. After all, Farage was effectively accused of incitement for saying we should feel ‘pure cold rage’ about the killing of Henry Nowak. The BBC even misquoted him as saying we should feel ‘pure white rage’ about the killing.

When it comes to Farage, Britain’s political and media elites will try to crucify him for things he hasn’t even said. Yet they remain very quiet when someone like Polanski, wittingly or otherwise, shares an image of someone wishing for the decapitation of a fellow politician.

Still, none of this can justify calling for the police to investigate a party leader’s social-media posts. The principle of free speech is simply too important.

Reform should know this. At its party conference last year, it platformed Lucy Connolly, the former childminder who was jailed over a social-media post published in the immediate aftermath of the Southport murders. Reform representatives rightly argued that she should not have gone to prison for her tweet, no matter how offensive it was. Reform also supported Graham Linehan when he was arrested by armed police at Heathrow Airport over gender-critical social-media posts.

In these cases, Reform was demonstrating a much-needed willingness to stand up to the policing of speech online. It needs to do so again when it comes to its political opponents.

Zack Polanski’s post was not incitement. The Green leader should not be arrested. And the police should find something better to do than poring through a party leader’s social-media accounts.

Luke Gittos is a spiked columnist and author. He is the author of Human Rights – Illusory Freedom: Why We Should Repeal the Human Rights Act, which is published by Zero Books. Order it here.