We knew the SNP wanted to break up Britain; what we didn’t expect was that David Cameron would decide to help the party. The SNP is confident that English Votes for English Laws (EVEL), which the Government pushed through the Commons this week, will be the beginning of the end of the Union.

Why? Because it consigns Scottish MPs to second-class status in the House of Commons and will, they believe, make Scottish voters even less inclined to support Westminster as the supreme law-making body for the UK.

The Government intends to give English MPs, sitting in an English Grand Committee, the power to veto any bills on matters such as health and education that are already devolved to Scotland. It is David Cameron’s answer to the so-called West Lothian Question: why should Scottish MPs have a vote in English affairs when English MPs have no right to vote in the Scottish Parliament?

But as every school student knows, all MPs are supposed to be equal in the unitary Westminster Parliament and have equal voting rights. EVEL will undermine that essential principle and put the Speaker in the invidious position of having to adjudicate from which votes Scottish MPs should be excluded.

This will certainly weaken the ties that bind the UK. But this isn’t just about Scotland. In fact, answering the West Lothian Question isn’t why the Tory Government is pushing EVEL through Parliament on a procedural motion. It is really about locking Labour out of any future government of the UK.

It may not look as if another Labour government is imminent, with Jeremy Corbyn struggling to control his divided party. But there will surely be one eventually, and it is likely that it will depend for its majority in the Commons on non-English MPs. Until the general election, Labour had 41 MPs in Scotland alone.

However, the next Labour Prime Minister could find that he or she is in office but not in power. This is because Tory MPs sitting in the English Grand Committee will have an effective veto on all legislation on domestic affairs.

Say Labour tries to repeal the Health and Social Care Bill 2011 that increased the freedom of private firms to bid for NHS contracts. MPs on the English Grand Committee could veto it on the grounds that this is an English only bill.

It would leave UK Labour ministers for health, education and justice unable to implement the policies on which the government was elected. How could any prime minister pretend to govern when he or she can’t implement their manifesto pledges over 85 per cent of the UK population?

There is a degree of unfairness in the present arrangements, certainly. But it is notoriously difficult to define what an “English” bill actually is because many have financial implications for Scotland. The 59 Scottish MPs rarely exert a decisive influence on English legislation in a parliament of 650 and the SNP has, in the past, withdrawn voluntarily from exclusively English votes.

Unfortunately, the Nationalists set aside their self-denying ordinance in July. Egged on by anti-hunting groups they couldn’t resist trying to put one over on David Cameron by threatening to vote against any attempt to restore hunting with hounds in England. But they also hoped this would goad David Cameron into pressing ahead with EVEL. For make no mistake, despite their howls of anguish, the SNP is rubbing its hands at this move. Party members think it is the beginning of the end for the Union.

The Government is trying to present EVEL as a mere procedural matter, but it is the most radical change to the constitution since the 1911 Parliament Acts that limited the power of the House of Lords to vote down measures passed by the Commons.

Ironically, it will arguably leave unelected members of the House of Lords with greater voting rights than elected MPs in the Commons. This is because there will be no equivalent to the English Grand Committee in the upper house and all peers will continue to be equal.

The only satisfactory solution to the anomalies of devolution would be a proper federal constitution with a reformed House of Lords, regional parliaments and a written constitution. That isn’t going to happen because there is no desire to go through this upheaval in England. Most English voters are quite happy with their parliament.

Instead we have the federalism of fools: a piece of constitutional gerrymandering which could make Britain ungovernable. It will go down in history as the most narrow-minded exercise in partisan constitutionalism in British history.