This week’s air traffic control disruption, apparently caused by a single malformed flightplan, has provided a painful demonstration of the law of unintended consequences.

Lem Bingley

Lem Bingley

The culpable body, National Air Traffic Services, has stated that its IT systems behaved as intended by failing safely – which will come as small comfort to the many thousands of stranded travellers, or the airlines that reportedly lost about £100m to the outage.

A key goal for any kind of safety-critical software is not simply to do what it’s supposed to do – it must also avoid doing what it shouldn’t do. In other words, testing before rollout should actively seek out both positive and negative outcomes. In general, finding positives is quick and easy, while testing for negatives is hard, slow and expensive. After all, there are so many more ways to go wrong than to go right.

As a result, it’s always tempting to skimp on negative testing, especially when a deadline or budget ceiling looms. In business terms, this is equivalent to focusing on rewards without thinking too hard about the risks – seldom a recipe for success.

I can’t help thinking along these lines in the face of the government’s promised changes to nutrient neutrality rules. While our industry may welcome the prospect of unlocking schemes stifled by Natural England’s interventions – and some may smile at Tory ingenuity in blaming the EU for housebuilding shortfalls – I can’t help wondering to what extent the negatives have been assessed.

One potential outcome – harm to habitats aside – would seem to be that yet more money will be extracted from developers to pay for improvements the water industry ought to be funding. Extra costs may go on to scupper just as many schemes as the new policy unlocks.

Nutrient intervention also seems unlikely to substantially lift the bleak prospects faced by smaller housebuilders, who need deeper changes to balance the risks and rewards they face. Mark Quinn, chairman and chief executive of medium-sized builder Quinn Estates, sums up the issues sharply: “In our planning system now you’ve got to be a political expert, a water engineer, a planning policy expert and an ecologist. You need such an enormous skillset that it’s now incredibly difficult to build houses.”

The Portman Estate’s chief executive Oliver Fenn-Smith recently outlined to me his frustrations at how often policy interventions in the property sector seem half-baked. “Residential leaseholder reform and the proposed abolition of marriage value will have an impact on property portfolios because, basically, it’s taking away from one investor [the freeholder] and giving it to another [the leaseholder]. It may well impact reinvestment in local areas because receipts will be less.”

He adds that enfranchisement laws have pushed his firm to rent out rather than sell homes, because leasehold sales now put the integrity of the estate in jeopardy.

Asked what he’d like to see from the next government, Fenn-Smith makes an eminently sensible plea: “First and foremost is working with the industry, to actually understand what we can contribute and what we do contribute. Get to know us rather than making assumptions [and] make sure that you’re not using a sledgehammer to crack a nut.”

In other words, unlike aeroplanes, property policies really need to be grounded.