Anyone who had the misfortune to be travelling westbound from London on the M4 last night will likely have been grateful for the information displayed on the overhead gantries telling them the motorway was shut on their side of Swindon. It gave them good notice to decide which alternate route to take nearer the scene.

Yet as they neared the alleged closure, all the gantries were blank, at least sowing the seed of suspicion that the motorway had reopened. No point searching for traffic info on the radio; this was Sunday evening and you’d be more likely to find little green men on the moon.

So as the last possible exit looms, what do you do? Get off a possibly entirely open motorway or stay on and spend your evening in a ten mile car park? The latter is unthinkable, after all the gantries may simply not be working, so you prepare to leave. Then, at the last minute, a gantry flashes into life proudly proclaiming it will take you 18 minutes to reach the Swindon exit. To a man and woman, they all joyfully cancel their indicators and roar on up the motorway. Half a mile later, they reach a wall of stationary traffic. The motorway is, indeed, shut.

Had this happened to me, you’d not be reading about it here as my blood pressure would have burst every artery I own. As it was, it was my wife and several thousand other poor sods whose Sunday evening was wrecked by some feckless buffoon pressing the wrong button.