Hold off the jibes and sighs over how much poorer Brexit Britain will be. Forget about the mendacity and slipperiness of Boris ’n’ Nigel. In the six months since the referendum these have been the clever arguments to make, the ones that fill the sophisticated newspapers and BBC discussions. But none answer the far simpler and much harder question: then what? What happens when 17 million people get the feeling they’ve been cheated?

That will be the most profound question in British politics, not just in 2017 but for many years to come. As the broken promises of Brexit pile up one on top of the other, so that they are visible from Sunderland, from Great Yarmouth, from Newport, what will the leave voters do then?

The pledges I mean aren’t the ones about how £350m will flood each week into the NHS, or those others that came out waving a Pinnochio-sized proboscis. I’m thinking of the promises that went far deeper. The vow to “take back control”. To stop being the human punchline to someone else’s macroeconomic joke. To – as our north of England editor Helen Pidd wrote last week – no longer live on crumbs, while others in London enjoy entire loaves.

The Brexiteers were explicitly offering voters a once-in-a-lifetime shot at changing the status quo. And before embarking on what has otherwise been a stiff-backed, fixed-grin, try-hard few months at No 10, Theresa May got it, promising “people voted for change. And a change is going to come.”

The forecasts are in, and they indicate Britain will suffer its first lost decade since Karl Marx was alive

Except change, in our new prime minister’s dictionary, just means more of the same. Admittedly, it is only six months into Year Zero and Britain is yet to start disentangling itself from Europe. But whatever is promised – hard or soft, red white or blue – it’s clear that the terms of Brexit will be dictated by Donald Tusk, Angela Merkel and the other 27 members of the EU, rather than by our dream team of May, Boris Johnson and David Davis. We can also see much else of what the next few years will bring. The economic plan for the rest of this decade has been laid out by Philip Hammond, and it equals austerity-lite – but for even longer. The forecasts for wages and living standards are in, and they indicate Britain will suffer its first lost decade since Karl Marx was alive.

More to the point, it’s not clear what May’s initial promises of a fresh start were worth. She steeled herself to call off the expensive disaster of Hinkley C – then meekly waved it through. She vowed to install workers on company boards – then the idea didn’t even make it on to a green paper. She promised to stick up for “just about managing” families, then allowed her chancellor instead to carry on slashing taxes for multinationals.

And then there’s foreign ownership of Britain’s infrastructure. Remember how May promised to scrutinise any proposed takeovers of such strategic assets as water, energy and transport? Well, last week, while the rightwing commentators were diligently huffing and puffing over Gina Miller at the supreme court, another kind of sovereignty was being covered on the City pages. The National Grid announced it would sell a majority of its gas pipelines to a consortium of largely overseas investors, including China and Qatar, and led by an Australian investment bank, Macquarie.

You may never have heard of Macquarie, but my guess is you’ve probably been one of its customers. The bank is known as the “millionaires’ factory” or the “vampire kangaroo” – and it owns a lot of the most prosaic parts of British life. You’ve been Macquaried if you’ve left your car in a National Car Park, or flown out of Glasgow, Southampton or Aberdeen or if you’re among its 14 million customers in Thames Water. And as of next spring, it will lead an international group with a 61% share in our biggest gas distribution network: that’s 82,000 miles of pipe, serving 11m homes and businesses across eastern England, the north-west and the West Midlands.

I have come across Macquarie before, through its handling of Thames Water, which some analysts cite as being among the greatest debacles in all of Britain’s history of privatisation. Just as with National Grid, it led a consortium to buy Thames. Two academics at the Open University examined the accounts between 2007 and 2012 and found that in four out of those five years, Macquarie and its fellow investors took out more money from the company than it made in post-tax profits. They crippled the firm with billions in debt, while Thames customers paid ever more in water bills and got among the worst service offered by any water company.

When I put these findings to Thames, its response was the email equivalent of a shrug: “Some years dividends exceed the years’ profits, sometimes they are less.” This was even while the company successfully managed to offload much of the cost and the risk for the Thames Tideway tunnel on to ordinary households.

The National Grid gas pipelines aren’t the only things Macquarie is set to get its hands on. Even while May was at her party conference at Birmingham talking about a country working for all, journalists were being briefed that the state-owned green investment bank would soon be flogged off to … you guessed it, Macquarie.

One of the canards about the referendum is that the decisive swing came from working-class voters furious at high immigration, and that therefore the primary issue that needs to be resolved in the next few years is who gets to stay in Britain and how. Whenever I hear that, I think of the voters I spoke to in south Wales just before the vote. True, all the leavers volunteered immigration as their main justification. But the longer we talked, in this area that remains almost exclusively white, the more it became clear that they were angry at something else – not the invisible refugees, nor far-off Brussels. One, Gareth Meek, told me: “I’m angry at the British government. They sold the country out. There’s nothing we own any more.” A multitude of frustrations, pushed through a binary vote.

What happens when Meek and his fellow voters realise that their vote for change – however loosely defined – means more of the same? When that call to take back control ends up with them playing the same old captive market, there to be ripped off by multinational capital. Who will take the blame then?