The radical Greens have left SNP and Yousaf paying a heavy price - Euan McColm

He’s one of the most divisive characters in Scottish politics. To some, he’s a hero of the radical independence movement, to others he’s a champagne socialist crank.

But even his fiercest political opponent would have to admit that Scottish Green co-leader Patrick Harvie is a remarkably successful politician.

He and Lorna Slater may front up a party that came fifth, behind the Liberal Democrats, in the 2021 Scottish Parliamentary election yet Harvie wields extraordinary power. Since former First Minister Nicola Sturgeon brought the Scottish Greens into power alongside the SNP, Harvie and Slater have pushed hard to focus the government on their priorities. If we look at the big issues that have dominated Scottish politics in recent month - reform of the Gender Recognition Act, the deposit return scheme, the proposed introduction of highly protected marine areas (HPMAs) - we see Green fingerprints on everything.

It is true, of course, that each of these issues has, for now, hit the buffers. But Harvie remains clear that The Scottish Government must challenge in court the Secretary of State, Alister Jack’s decision to block Holyrood’s reform of the GRA on the grounds it would negatively impact on the UK-wide Equality Act. This is a position from which First Minister Humza Yousaf does not deviate.

Harvie may not currently be getting the policies he wants but he’s very much getting to do the politics he likes. The co-leader of the Scottish Greens is now the most powerful figure on the radical nationalist left.

Recently, Robin Harper - former leader of the Scottish Greens and the party’s first MSP - announced his decision to quit the party. The Greens had lost their way, he said, and he’d be voting Labour at the next election. Cue various Labour sorts popping up across social media to reflect on the wisdom and compassion of the man.

The truth is that pro-UK Harper has been semi-detached from the Greens since party decided, in advance of the 2014 independence referendum, to campaign for a Yes vote.

Harper may feel the Greens’ obsession with independence has diverted the party from its environmental mission, but he lost the constitutional argument long ago. Harvie’s (and Slater’s) Greens have seized the gap in the political market created by the implosion of the socialist left.

Even those Tory MSPs who shudder with rage at the very mention of Harvie’s name would have to concede he’s been responsible for some deft manoeuvring.

In his high public departure from the Greens, Harper raised concerns about the party’s position on Trans issues. Under current management, only full and vocal support for the complete reform of the GRA is acceptable. Members must be expected to support the introduction of self-ID and, if they do not, they should expect to be invited to leave.

Again, this is an argument Harper lost long ago. He might have legitimate concerns about the difficulty in frankly discussing gender issues, but the party is where its activists want it to be on the GRA.

Robin Harper may level the charge that the Greens have lost their way, but the defence is a strong one: this tiny party is in government and frequently drives the political agenda. If those are the consequences of losing one’s way…

But what is good for the Greens is not necessarily good for the SNP.

When Ms Sturgeon brought the Greens into government with the signing of the grandly titled “Bute House Agreement”, there was much talk of the SNP wishing to burnish its environmental credentials, but the truth was that she was motivated by fear that ministers in another minority administration might be vulnerable to votes of no confidence.

In return for the support of Green MSPs, the party received two ministerial roles. Remarkably, the Greens were able to negotiate themselves out of collective responsibility on a number of environmental and economic issues.

The campaign to replace Sturgeon as SNP leader revealed the depth of unease within the party about the impact of the deal with the Greens.

Humza Yousaf, who scraped to victory, spoke supportively of the agreement throughout his campaign but challengers Ash Regan, who called for it to be ripped up, and Kate Forbes, who thought it worth revisiting, won the support of half of their party.

Former minister Fergus Ewing, a member of the SNP’s dwindling but until recently substantial right-wing, has been characteristically outspoken, dismissing the Scottish Greens as “wine bar revolutionaries” and calling for the coalition (they say it’s not a coalition, but it is) agreement to be put back to the nationalists’ members.

Ewing is fairly easily dismissed by those and such as those in the SNP. He’s yesterday’s man, out of touch.

The intervention by Kate Forbes - seen as many in the SNP’s ranks as a leader-in-waiting - on the subject is not so blithely swept away.

Forbes’s suggestion that the Bute House Agreement should be discussed as part of a “check-in” with members suggests scepticism about the value of the Greens is not confined to the fringes.

If there were to be a leadership contest tomorrow, Forbes would be the likely favourite to win. She speaks for many in the SNP.

In September, the Scottish Government will challenge in court the decision of the Secretary of State to put the brakes on Holyrood’s reform of the GRA.

The First Minister would like us to see this as an example of the SNP defending democracy. The trouble is the majority don’t support reform.

The storm to come will be good for the Greens. They’ll be the radical force supporting the marginalised and so on.

But, with mainstream voters opposed to the new gender legislation, the price to the SNP may be heavy.

It’s little wonder some Nats want to break-up with the Greens.