Liz Truss had barely finished speaking when the ripples began spreading around the chamber. Notes were ferried along frontbenches; brows furrowed, faces paled and Keir Starmer quietly slipped out. It swiftly emerged that family members were being summoned to the bedside of the 96-year-old Queen, so visibly fragile just a few days ago as she anointed her third female prime minister. What a sombre, black-edged week for a new prime minister to make her debut, and not just because of darkening skies over Balmoral. The energy plan Liz Truss was unveiling when the news broke of the monarch’s failing health essentially involves writing a blank cheque for multiple billions for the next two years, to cover the costs of something she cannot easily predict or control. It is an extraordinary gamble with particularly serious consequences for the poor, for the public finances and for the planet. If it blows up in all our faces, it’s hard to see her government recovering. But if she can somehow pull it off, then nobody will care that the abiding image of her first speech as prime minister was of a binbag shrouding a rain-sodden lectern, or that she once made a duff speech about pork markets. People often complain that politics seems petty and superficial, fiddling round the edges. Well, be careful what you wish for. The era of big ideological divides, big politics and equally big risks is back, under a prime minister now boldly staking all her roulette chips on taking Britain into the red. The pandemic forced Boris Johnson into some equally momentous decisions, but his differences with Labour over lockdown were mostly over timing. Now, two diametrically opposed economic theories of the world are duking it out in real time: Truss’s conviction that tax cuts are the key to growth, and that the resulting wealth will somehow trickle down to everyone rather than accumulating, as it so often does, in the pockets of the rich, versus Keir Starmer’s argument for redistributing wealth via windfall taxes. What’s more unexpected is that somehow Labour has overnight become the party of soberly balancing the books, or finding ways to pay for the things you want to do, while Truss seems content to cross her fingers and borrow her way out of trouble. The idea of piling anywhere up to £150bn on the never-never would surely have Margaret Thatcher turning in her grave. The jury is still out on what it will do to her successor, with Truss’s statement on Thursday notably kicking some difficult questions a few weeks down the road. Household bills will be frozen for two years, at about £2,500 for the average home, while businesses and public sector organisations like hospitals and schools get an equivalent deal for six months (after that, only vulnerable people will be supported). But Truss wouldn’t be drawn on costings, or exactly where that money will be found: we must await a budget later this month for all that. There will be more licences to drill for oil and gas, and the ban on fracking will be lifted, despite fierce local resistance in areas rich in shale gas. But further decisions on climate policy seem to have been parked under a review, led by the thankfully pro-green former science minister Chris Skidmore, of how to hit net zero without sacrificing economic growth. Truss offered nothing much for those who have been struggling ever since bills went up last April, never mind this winter, and there was little mention of the urgent need for insulating homes to cut bills – although that may also have to wait for the budget. And the question of whether there will be blackouts this winter, if Russia continues to starve Europe of gas supplies, still hovers. As a libertarian who hates the idea of the state telling people what to do in their own homes, Truss has ruled out rationing fuel and won’t be ordering anyone to turn down their thermostats. But her government has put itself on the hook for whatever we spend this winter, it has a huge new incentive to keep fuel usage low, and talk of a campaign encouraging Britons to cut their energy usage is to be welcomed. There is a golden opportunity here for Truss to treat decarbonisation like the national war effort it should always have been: repackaging the idea for people who would normally balk at anything too green-sounding as a patriotic way of defying Vladimir Putin and protecting their children and grandchildren from the long-term bill for this crisis. Can it be beyond a Conservative government to rustle up a bit of blitz spirit around the idea of pegging out the washing instead of tumble-drying it, getting your cavity walls filled or not running too many appliances at times of peak pressure on the National Grid? When Ukrainians are dying in their thousands in the name of a free Europe, being asked to put the dishwasher on a bit later at night or turn off your hot tub doesn’t seem an outrageous sacrifice. Many people who haven’t previously bothered much about their bills have been shocked into using energy more mindfully in recent months, and it wouldn’t take much to encourage some benign new habits, which could stick once this crisis is over. The long-term consequences of all that borrowing, however, may prove a harder sell. Truss is already facing rumblings of protest from free market thinktanks such as the Institute of Economic Affairs. Polling for the campaign group 38 Degrees suggests most Tory voters would rather the bill freeze were funded via a windfall tax than borrowing. For now, most people will just be relieved not to face £6,000 bills next spring. But if all this splashing of cash triggers a sharp rise in interest rates, the mood could darken very quickly. The tottering pile of cards that is the British property market is built on cheap borrowing, and interest rates that were so low, for so long, that a whole generation of homeowners have virtually forgotten they can go up. Some who stretched themselves to the limit to buy in recent years would surely snap. Renters would feel the pain, too, if buy-to-let landlords tried to pass the cost of their own rising mortgages on to tenants in the form of even higher rents. The stakes are high, the risks real, and the outcome not wholly in British hands. This has been a consequential week in the life of a nation, one whose unfolding dramas are likely to stick in the memory for some time. We may yet have to endure more of those before the winter is out. Gaby Hinsliff is a Guardian columnist