If you were about to undergo surgery, you would expect to know what the operation involved and to be informed about all the risks and benefits. It's called informed consent and no decent surgeon would go ahead without it.
Brexit certainly is major surgery with far-reaching consequences and the government is about to proceed without informed consent.
At the time of the referendum the choice was simply to leave or to remain. The type of Brexit was not on the ballot paper, which is like a surgeon asking their patient to consent to an amputation in two years' time without either of them knowing whether this would involve a few toes or their whole leg.
Voters were assured that this would be the easiest deal in history and that the world, including the EU, would be queuing at our door to trade on our terms. There would be cake and we would be eating it, alongside every fish that swam in our waters.
In the real world, instead of a bespoke deal we are all being marched briskly to the edge of the cliff. No deal and no transition look increasingly likely to be the outcome, and is the preferred option of those MPs who have deliberately and fatally undermined the Chequers plan.
The surgery looks set to be far more radical than anything set out in the referendum and the side-effects and complications of a hard, walk-away, no-deal Brexit with no transition are very different from the promised targeted surgical excision of just the parts of the EU that the Brexiteers didn't like. Shouldn't people have an opportunity to weigh up the risks and benefits before proceeding?
Once we know the final terms there is not just an opportunity but a duty to set out the unintended consequences as well as the potential benefits. There is a compelling case for that to be followed by a people's vote: we have to make it clear to government that it should not embark on potentially ruinous surgery without the informed consent of the British people.
It might be that a majority nevertheless decide to proceed, but there is no democratic mandate for Brexit until the choice is clear and an informed decision can be made. If the hard Brexiteers are confident about their walk-away, no-deal scenario they should be happy to agree.
The polls show that public opinion is turning on Brexit, especially as the sheer scale of the cost and consequences becomes clearer.
No responsible government should countenance deliberately and knowingly inflicting such economic and social harm on its people before at least checking that is what they really wanted.