The SNP-Green Bute House “Don’t-Call-It-A-Coalition” Agreement had everything going for it. Two parties which agreed on so much – their nationalism, their shared suspicion of business, or their centralising policies like HPMAs – should have had the best possible chance of maintaining their government through an entire parliamentary term. If there were such a thing as an “easy” coalition, this really ought to have been it.

That the SNP and the Greens nevertheless fell apart with such acrimony and discord makes their failure of governance all the more damning. At the first sign of meaningful difficulty, both parties showed that they were not up to the challenge.

When the news came out on Thursday, one of my constituents noted wryly on social media that it was, in fact, good news for the Greens: “They won't have the responsibility of creating legislation and laws that can actually stand up to any sort of scrutiny”.

He was right. The Scottish Greens had ministers in office. They enjoyed the trappings of power and policymaking. They voted in lockstep with the government – but they did their level best to deny responsibility for the government they shared with the SNP. For being in both government and opposition at the same time they had learned from the SNP who had been masters of the craft for years.

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Humza Yousaf: how long before his enemies turn on him?

It is far easier, politically, to be outside of power than to take responsibility for your decisions. That is why the SNP themselves have always insisted that they are not really in power when asked to account for their government – but political expediency makes for bad governance.

All governments are a sort of coalition. Whether they are made up of multiple parties or just one, there are always competing interests, personalities and priorities. Forget Cameron-Clegg or SNP-Green; Tony Blair and Gordon Brown formed their own intra-Labour coalition for ten years, one that was extremely successful (until it wasn’t).

I can speak to the challenges of coalition from some experience. I served in the Coalition Government in Westminster from 2010 to 2015. A coalition between liberals and conservatives would be hard enough in the best of circumstances. Holyrood is designed to produce coalitions. The House of Commons is not. Having been Liberal Democrat Chief Whip for three-and-a-half of those years I could write a book about it (but probably only publish it posthumously!).

From day one, the collapse of the coalition was predicted. Every disagreement (and there were many) was cast as evidence of impending failure. It would only last a month, or three months, or six months – and so on. Eventually the clever people realised that it was going to last. The disagreements continued, but the predictions of failure stopped. The obvious point about all of this is that coalitions are hard. They involve uncomfortable compromises, defending partners you do not really want to defend, and enacting policies that, at best, would not be your first choice to implement.

The cliché goes that “to govern is to choose”. Political accountability can be a painful thing – but there is no point in being in politics if you cannot step up to government when the moment arrives. Whatever criticisms can be levelled at my party for our time in government, I do not regret that when that challenge came our way, we stepped up to it and took political responsibility.

The SNP and the Scottish Greens had some of the most favourable terrain you could imagine to allow their coalition to succeed. Humza Yousaf may have expelled his coalition partners, but their shared failure suggests that neither party is fit for government any longer.

Alistair Carmichael has served as the LibDem MP for Orkney and Shetland since 2001