Here’s what John McDonnell should have promised Labour would do in his car crash conference interview

It’s tough to watch the official opposition fall apart on screen. At this year’s Labour Party Conference, the atmosphere is so febrile that the media has cameras trained on the faces of every rebel MP or reluctant Jeremy Corbyn compromiser, waiting patiently to record the barest flinch or twitch that gives away their true feelings. See, for example, the footage of Clive Lewis after realising his speech on Trident had been tweaked before delivery by HQ. And there is no need to rely on TV cameramen to do the dirty work – every single person in that room is carrying a smartphone ready to record the latest rift.

One expects they caught a phantasmagoria of gurns and grimaces yesterday evening, when John McDonnell was grilled by the BBC for Newsnight on the evening of his conference speech as shadow Chancellor. He made, let’s not obfuscate, an almighty watch-between-a-web-of-your-own-fingers mess of it. Pushed on tax and other points of basic fiscal policy he had no definite answer. It was squirm inducing.

Yes, Corbyn has only just regained the Labour leadership. Yes, we are still (officially) four years out from a general election. On paper, at least, there is time to flesh things out. Except, for a leader who has already been in post for a year and whose victory last weekend was well predicted, these remarks feel remarkably like the ones the Shadow Cabinet made in television interviews 12 months ago. And that election that is four years away might actually be called as early as May 2017.

Do voters want yet another taskforce or inquiry? Is there appetite for further review of policy? No. What Labour supporters are crying out for is not more collaboration but leadership and clarity, not endless debate around the edges.

So, with certainty in mind, here are six steps that McDonnell could take to right now to give voters certainty and without splitting his party into a million tiny fragments.

There is no need for a full-blooded land value tax to replace all other forms of revenue via taxation, as the most ardent campaigners want. But a tax on the value of land would reintroduce a level of fairness into the housing market, stop developers hoarding land without building new homes, would remove the confusion and general moral outrage about inheritance tax and help fund public services. It is a lot simpler to understand and easier to pay than capital gains tax or stamp duty, and helps reconnect people to the real value of the assets they own. It need not be unpopular if it is marketed in positive terms (now your children automatically inherit your home with no interference from the state).

It is a disincentive to property speculation, with amateur landlords – often the least reliable – eased out of the market, and would help prevent tax evasion and avoidance schemes which use complex property portfolios to hide wealth. You can’t hide land, after all. This is a straightforward measure that actually sounds far more radical than it really is.

Don’t say you will hike up the basic rate of income tax for anyone earning over, say, £200,000. Sure, that’s what he wants to do – but it will only lead to strife. The usual individuals will come out of the woodwork claiming that it’s a cap on aspiration, a drain on business and so on.

Few people in Britain earn that much, sure, but the ones that do are relatively influential when it comes to the health of the economy, so play nicely. So don’t tax the wealthy on their earnings, tax them on the spoils of wealth, on the frivolous and unnecessary purchases they make with it – jewellery more than £500,000, million-pound yachts, and the like. (And you’re already taxing the Mayfair mansion more effectively now you’ve got an income based on land value.)

At the other end of the spectrum, commit to scrapping the Conservatives’ failed universal credit programme which, instead of simplifying the benefits system, has only served to make it more unworkable and more cruel, in a truly Orwellian manner. It is impossible to track every hour of work that each claimant has, and trying to do so removes the trust between state and benefits recipient. Scrapping this scheme will actually save money, not waste it, and it will bring some stability to the lives of hundreds of thousands. If you want something more radical in the back pocket, promise a review into the feasibility of replacing the entire benefits system with a more simple and straightforward universal basic income policy. Though I’m an advocate, that’s the one to kick forward.

This policy was never about serious financial savings but all about political positioning. So it doesn’t cost much to just overturn it. It’s a sign that Labour is still committed to universality and giving all children the same start in life – a useful message when the row over grammar schools is beginning to engulf the Tories.

The most embarrassing moment of last night’s Newsnight interview was McDonnell’s refusal to put a figure, however tentative, on the percentage of public expenditure that would come from tax, settling, in the end, for the muddied compromise of “roughly the same as it is now” – which is what, exactly? Just come up with a number. It doesn’t matter if it needs to change; the economy shifts all the time – there will be plenty of plausible excuses if you need to change your mind before the printing of the manifesto. Just say something decisive.

And finally… for God’s sake just say you will renew Trident. Thousands of jobs and the already critically damaged relationship between Scotland and England are at stake. As Labour MPs are already allowed to vote with their conscience on this matter – at which point Corbyn and McDonnell can do the same, or abstain – the policy must reflect the most sensible economic position for Labour and its members. There is little damage that can be done by voting against party policy when the wider public are already well aware that this is a key issue on which the leader and those he leads (and those voters he represents) disagree.