Last month’s political TV debates at home, and volcanic quakes overseas, are both dramatic cases in point; and the emergence of a credible third choice for government in the UK could prove just as seismic as the eruption of an ash cloud across European airspace.

One-off, unprecedented events can trigger unexpected consequences whose impacts are more widespread and longer term than probability would allow. Last month’s political TV debates at home, and volcanic quakes overseas, are both dramatic cases in point; and the emergence of a credible third choice for government in the UK could prove just as seismic as the eruption of an ash cloud across European airspace.

The big recent question for retailers is the extent to which changes to consumer behaviour that were generated by the recession will outlast it. When the boom times are here again, will we just revert to the status quo ante or have we permanently found new ways to behave?

A similarly big political question is now being asked: would a hung parliament and an empowered third party simply be dressing old Westminster in new (for some, flimsier) clothes, or might they transform the body politic in shape and strength for decades to come?

Now that the planes are flying again, we must also question if the movement of people and goods across Europe will revert to normal, or if new processes have been set in train.

Although the flight ban lasted less than a week, its repercussions could rebound for years. The travelling public, especially those who (actually or vicariously) have been disadvantaged, many at significant expense, might think twice about flying next time. Low-cost could become a real misnomer, for operators and passengers alike. European boats and trains could regain popularity and their environmentally friendly credentials bring a feel-good bonus to their users, for many of whom sustainability alone was never enough to dissuade them from polluting the skies.

The movement of goods was equally affected. Fast fashion, fast food and instant messaging define the pace of today - and we demand that providers deliver at the highest speed. At the same time, the middle classes have entered an age of dilettantism in which the exotic has become the quotidian and summer products are expected in winter too. The hiatus in air freight caused temporary havoc to retail and consumer fulfilment. Maybe now supply chains and consumers will acknowledge the vulnerability of speed and seasonality and accept more freight by rail, road and sea - sustainability, once again, the winner by default.

Last month, the World Retail Congress fell horribly foul of the flight ban and Berlin was rather empty, but it made strolling round the sixth floor of KaDeWe a greater, less-crowded, pleasure than usual. However, the magnificent Fischkutter bar remained packed out. “How,”

I asked, “can you maintain such a selection of fish in this land-locked, now air-shut, city?” “Because our fish is frozen,” was the reply. As a self-confessed gourmet, I always thought the best fish must be fresh fish. No longer. Fish, if properly frozen (or even salted) when caught, can taste better than so-called fresh, and not-by-air transportation is as sustainably sound as the fishing itself needs to be. And whence does much of this fish come? Why Iceland, of course.

Michael Poynor, managing director, retail expertise