The Syria vote was a triumph of parliamentary sovereignty

Votes such as last night's are no longer mere rubber stamps but a binding convention that can change the foreign policy of a government.

There are several significant angles to last night's Commons vote on Syria. Foreign policy experts look at Britain’s role in the world and our relationship with the United States; domestic politicos look through the prism of party politics, asking who came out better between Miliband and Cameron. Meanwhile, Syria continues to suffer and we can only now hope that inaction is the lesser of two evils.

But amid the fallout, easily obscured by the more obvious issues of the day, is a seismic shift in the British constitution, an evolution that has crept up quietly but which serves to empower Parliament and constrain the executive. 

While the Prime Minister officially retains the Royal Prerogative to declare war, it is clear that this power is now tempered by the convention that Parliament must vote on the matter beforehand.

Previous votes on Iraq and Libya, while contentious, saw the government of the day validated by the Commons. Before this it had been understood that the executive had a right and duty to declare war as it saw fit. The real test of this innovation was whether a government convinced of the need for military action would respect a vote that opposed it.

The fact that Cameron had to promise the House that it would have a second vote, the fact he has now changed course so dramatically – while retaining the right to declare war - shows that votes like this are not simply rubber stamps but have become a binding convention that can change the foreign policy of a government.

Ironically, by calling an unprecedented vote on Iraq, Tony Blair, the most presidential of prime ministers, set in place an innovation that created a precedent largely devolving 'war powers' from the executive to the legislature.

Frustrating for many, our uncodified constitution is nevertheless pragmatic and far from conventions being ignored (as many fear has increasingly happened) a new one that curtails government power has clearly entrenched itself.

In the Lords, former generals, admirals, defence secretaries and ambassadors urged caution, while the debate in the Commons was marked by many MPs speaking of their constituents’ concerns. Some cheap politicking (from both benches) aside, the standard of debate was high and the tone respectful.

Whether one agrees with the outcome or not, the vote was a reassertion of Parliamentary sovereignty – a message to the executive, but also to the United States, that in the United Kingdom it is with Parliament, not the Prime Minister, that ultimate power resides. Indeed, many MPs spoke of this as a retreat from British presidentialism and a return to the PM being primus inter pares.

It is now unthinkable that Cameron would disregard Parliament’s wishes. Likewise, his deference to the Commons and his claim to have listened further entrenches the precedent that any future Prime Minister would have to call a similar vote on military action.

In my view, reserve powers of Royal Prerogative should remain with the Executive in case a Prime Minster must act immediately before explaining himself or herself to the House. But it is now clear that any premeditated military action will rightly require the approval of Parliament.

The British constitution is something that has grown organically over the last thousand years. It has survived because it has evolved; its imperfections have been mitigated by its flexibility. This latest stage in its evolution has something to say of our present and of our past. It speaks to a country disillusioned with foreign interventions, war-weary and cautious of unknown consequences. But fundamentally it also reasserts an ancient British principle: Parliament is sovereign.

James Hallwood is associate director of The Constitution Society @jhallwood

"A message to the executive, but also to the United States, that in the United Kingdom it is with Parliament, not the Prime Minister, that ultimate power resides". Photograph: Getty Images.

James Hallwood is associate director of The Constitution Society @jhallwood

How Jim Murphy's mistake cost Labour - and helped make Ruth Davidson

Scottish Labour's former leader's great mistake was to run away from Labour's Scottish referendum, not on it.

The strange revival of Conservative Scotland? Another poll from north of the border, this time from the Times and YouGov, shows the Tories experiencing a revival in Scotland, up to 28 per cent of the vote, enough to net seven extra seats from the SNP.

Adding to the Nationalists’ misery, according to the same poll, they would lose East Dunbartonshire to the Liberal Democrats, reducing their strength in the Commons to a still-formidable 47 seats.

It could be worse than the polls suggest, however. In the elections to the Scottish Parliament last year, parties which backed a No vote in the referendum did better in the first-past-the-post seats than the polls would have suggested – thanks to tactical voting by No voters, who backed whichever party had the best chance of beating the SNP.

The strategic insight of Ruth Davidson, the Conservative leader in Scotland, was to to recast her party as the loudest defender of the Union between Scotland and the rest of the United Kingdom. She has absorbed large chunks of that vote from the Liberal Democrats and Labour, but, paradoxically, at the Holyrood elections at least, the “Unionist coalition” she assembled helped those parties even though it cost the vote share.

The big thing to watch is not just where the parties of the Union make gains, but where they successfully form strong second-places against whoever the strongest pro-Union party is.

Davidson’s popularity and eye for a good photo opportunity – which came first is an interesting question – mean that the natural benefactor in most places will likely be the Tories.

But it could have been very different. The first politician to hit successfully upon the “last defender of the Union” routine was Ian Murray, the last Labour MP in Scotland, who squeezed both the  Liberal Democrat and Conservative vote in his seat of Edinburgh South.

His then-leader in Scotland, Jim Murphy, had a different idea. He fought the election in 2015 to the SNP’s left, with the slogan of “Whether you’re Yes, or No, the Tories have got to go”.  There were a couple of problems with that approach, as one  former staffer put it: “Firstly, the SNP weren’t going to put the Tories in, and everyone knew it. Secondly, no-one but us wanted to move on [from the referendum]”.

Then again under different leadership, this time under Kezia Dugdale, Scottish Labour once again fought a campaign explicitly to the left of the SNP, promising to increase taxation to blunt cuts devolved from Westminster, and an agnostic position on the referendum. Dugdale said she’d be open to voting to leave the United Kingdom if Britain left the European Union. Senior Scottish Labour figures flirted with the idea that the party might be neutral in a forthcoming election. Once again, the party tried to move on – but no-one else wanted to move on.

How different things might be if instead of running away from their referendum campaign, Jim Murphy had run towards it in 2015. 

Stephen Bush is special correspondent at the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to British politics.

0800 7318496